But I have seen somewhere that Google allows students with max one year gap.but I have twice.so please tell me about that

See the truth is, if you manage to get to the top IITs or NITs then nothing matters. Just maintain a decent CGPA and there should not be any backlog thats what they see. But if you are a dropper and taking admission in Tier-2 or 3 college then your drop will be considered by the companies visiting there.

But I may get cse in nit suratkal after two year drop in jee.am I eligible to apply for Google after completing btech decently as I have seen somewhere Google doesn't want more than one year education gap.is it true??

I told you that if you are in top college then it doesn't matter. During the placement session if the company visits your college they will ask you the reason for your dropping. You can tell them about your preparation for JEE. And after much preparation you are now in this top college.
ONE important thing to note is, does Google comes to your college during placement session?
If you are applying for off campus placement then you may face problem.