How can my ex-wife revoke my visitation? She does this every other weekend when I'm suppose to get her. She only does this because she hears a rumer or it just because she don't like me.

If you have a court order stating that you are to get visitation for a certain period or at certain intervals, she CAN NOT simply revoke your visitation. If she is doing so and you have a court ordered (or at least it's included in the custody order) visitation plan, then she is in violation of that court order.
If you have an attorney, I would contact them and have them bring it back before the judge.

She does it because you allow it, if she does it, you take her back to court and see if the judge will hold her in contempt for not following the court order. See if you can arrange though the couirt for a 3rd party to pick up the children or for her to turn them over to, if there is an issue with you and her.

She is doing this because you have been allowing it to happen

The only way she could do this would be if she were the judge of your case and her case. It sounds preposterous and is preposterous. I can understand that you might get mad enough to disrupt the peace, but please don't do so. As a previous poster said, your visitation is either by agreement with her, or by order of the court. You need to get that cleared up quickly. Which is it?