Is the Byzantine army similar to Chinese army in many aspects including tactics and organisation?Or at least closer to Chinese army than any other armies of European origin at that time?
Just for comparison only...

Yes they were. Apparently the Tang armies and contemporary byzantine armies had similar tactics and weapons. The following quotes are from a book called "Medieval Chinese Warfare" by David Graff, discussing among other things the tactics recommended by the chinese general Li Jing who lived in the 7th century:

"The contents of Li Jing's manual are remarkably similar to what we find in Byzantine military treaties such as the Strategicon... It shows the same concern with battle formations, marshing order, camp layouts, scouting, and discipline. Some prescriptions are almost exactly the same."

And in another chapters Graff writes:

"For the most part, the military tools and techniques of medievel China would have been familiar to a Byzantine visitor (and vice versa). The level of military technology was essentially the same. Both Chinese and Byzantine armies relied on upon a cavalry composed of both mounted archers and armored lancers as their main strike force, but supported this with infantry armed with spears, swords and bows."

Hope this helped

Mind you, most armies are very similar.........

However, Graff didn't mention that there are some weapons in the Tang army which wasn't in existence in the Byzantine(at the time), one of them is the crossbow, the other is the Modao. The armour design of the two armies is also somewhat different.
Tactically, Byzantine had a larger proportion of their army as cavalry, about half, while in the Tang army the number is only around 1/5-1/3.(exceptions are in campaigns against nomads).

Because of this, Tang's infantry also tend to play a more offensive and decisive role in battle, while the Byzantine army is more similar to the early AOF army in that the infantry is mainly a defensive base of operation, advancing only at the right time.

The Byzantine armies infantry is based on legion like sword and sheildmen with javelins and spearmen,I think Tang infantry is more archery based?

The Crossbow in Europe was a greek invention and used by the Romans. It woud be utterly strange if the Byzanthian army would not have used them at least at a small scale for siege operations. Google "Gastraphetes".

I was talking about the hand held battle crossbows, which the Byzantines didn't have.

Both the Romans and Byzantines had them, however they were extreemly rare. However large scale crossbow use (with Western European style weapons) did exsist for the last 250 years or so of the Empire.

Graff's comments are a bit glib. I suspect they are based on the numerous similarities between Byzantine manuals and Chinese ones (and Persian, Arab, Indian ones etc...)

The comparison here is within the frame of the Tang era. And I already mentioned there are some weapons in the Tang army "which wasn't in existence in the Byzantine(at the time). " The Arab army at this time is actually quite different, their early armies emphasized on infantry, usually mounted on camels. Their major riders were light cavalry, not heavy. Even after they adopted heavy cavalry from Byzantine and Sassanids, it remained largely defensive, lacking the shock initiative role of the heavy cavalry users. I am not aware that India had any military manuals at this time, in fact a comparison between Tang and Byzantine may simply have to do with the fact that military manuals are written at all compared to other states without a documentary historical tradition. The fact is warfare of the time is most likely remarkably similar, any variant has more to do with the social organization and financial capability of the states as well as minor technological innovations with certain tactical advantages.

Even Sassanids persias military had a manual which was remarkably similiar to the Byzantines. Byzantine infantry was mainly used as a position where the cavalry could fall back on and reorganize.Not as shock infantry like the Tang dynasty troops who attack.

Indian manuals are comparable to early Chinese and are often very detailed (eg Arthashastra http://projectsouthasia.sdstate.edu/Docs/h...astra/BookX.htm a later one from c. 200 BCE but very interesting.)

It's fascinating how military minds from many different cultures converge on similar methods, strategies etc. Gives the impression that there are basic fundamental issues they each discovered.

forgot the main bit....

Contemporary Byzantine and Tang armies relied on composite bows (as time progressed a greater proportion of Tang militia units were massed crossbow)

The Tang actually relied just as much on the crossbow as the composite bow, there was an equal proportion of them in the army. This has not changed.