I take care of some street dog and two days back one of them had a nasty bite on thigh of a hind leg. It is about half inch deep and recently I have seen there are some maggot inside the wound and the dog is relentlessly licking that place. He has reduced his food intake and started limping.
I have been giving antibiotic powder in side by all are being washed during licking. I want to kill those maggots but the wound is so deep that it is not possible to get the access to that specific place. Some one asked me to use turpentine oil to get rid of those but still I am looking for some suggestion.

Ahhh no, do not use turpentine, that would burn like you wouldn't believe!

Why haven't you taken the dog to a vet?

It sounds like it definitely needs stitches, and if there are maggots then the wound will need to be properly cleaned, and any dead tissue removed.

You have ended up making this cost a LOT more by not taking your dog to the vet as soon as the wound appeared.

I would suggest a vet as well... I know it isn't your dog, but at least take it to the SPCA, if you are going to feed this street dog, then he is coming to you to look after him.
Turpentine... you not such a good idea. I really don't think there is going to be a successful way for YOU to kill the maggot. Are you sure it's a maggot? Usually Maggots would eat the rotted flesh, but do you live in an aera where Bott flys are? It could even be a wasp Larvae, which will be extremely painful as it matures. If you don't have the money, go to the vet, ask THEM what you can do. They may treat the dog anyway. Call your local Humane Society, call your local shelters, call the pound if you have to. But obviously this dog is hurting, he needs help.