he paid domain 2 years, changed the c-Panel code, keep related informations in the dark for long while and back to his country now, he refused to tell any and said these all not company property, he paid, belong to him; what should i do?

The kind of business where someone from HR anonymously solicits legal advice from a local social networking forum.

The company should puchase its own domain and not leave it up to web development staff to pay expenses out of their own pockets.

...

Hahahaha ... 兽 is not too far from the truth ... and this sounds too much like "blackmail" ...

If the business is "loose" enough to have someone, or anyone, taking ownership of their confidential info as well as their domain, and now facing "trouble" to get them back, my guess is that the business is not really huge, and that they cannot afford to buy these back ... on the other hand, this guy might be thinking about running his own business using this information and domain ...

So my answer, keep negotiating ...