I have a wild cat. She had babies and the male always comes to kill them so I have to be there when the mom is not. I want to have the mom cat as a pet And the babies too but how to get her.

Food is the key to a cats heart.

We had a stray that we took in a while ago. She was completely wild when she had her kittens, we just put a plate of food down and then sat about 20 meters away.
She was hesitant at first but she eat the food and eventually became comfortable with the distance between us and her.
This was when we moved a little closer.
She got used to that.
Eventually we were able to sit right next to her and even pet her while she was eating.

Now her kittens are all grown up and have loving homes. She still lives outside... well, under our house actually but she is very friendly and lets us pick her up and pet her while she purrs away.