i mean to ask just abt secure way while dealing person to person cash transaction
It's difficult to answer that because there is no such thing as a perfect way to make such a transaction. It all depends on the risks you want to minimize but nothing is absolutely perfect.
Some risks that I can think of are:
1) The person could run away without paying your bitcoins
2) The person could try a double spend
3) The person could assault you and steal your money
4) The person could take your cash and claim you did not send him the BTC and it will be difficult to prove that you did
There could be many other possibilities that we don't think of but in my mind it's no different than dealing with someone at a convenience store. You just have to use common sense. If there are any specific risks that you're afraid about then you should mention that here so that you get the appropriate answer.