I have Green card .I want to know as to how long can you stay out of US without any risk to my Green card status ?Some one tells me that I cannot stay out of US for more than 365 days while otherone tells me that it is not true .

Permanent residents can generally stay outside the US for up to 6 months without too much of a problem. It is very fact specific and depends on your ties to the U.S. In the US, do you have a house, a vehicle, ongoing employment, family members, bank accounts, insurance, credit card accounts, club memberships, etc. are you paying taxes annually?

You are asking about " any risk", so be advised that even a short period, say several months could be a problem if you do not have evidence of ties to the US. If so, it would be better for you to apply for a re-entry permit, I-765. You need to be physically present when filed and for the biometrics.

Good luck.