I get position of a object of last and current frame .then get a ray.detect the ray and wall. if intersect, get the point of intersect.and then move the corner of object to the point. this is my collision process.but I am afraid something wrong will happen because of float error. so maybe I move my object to the point of intersect, and the object could slightly penetrate the wall because of float error.so this will affect successive calculating and then will create error.

Numerical error is almost inevitable in collision detection, and you have to find ways to work around it. A common solution to the problem you describe is to not move the object all the way to the contact point, but rather just short by some small distance. Even then, you may encounter problems elsewhere. The fact is that implementing collision detection robustly can be quite difficult.