Gravity is not enough to consist a galaxy, some physicists put forward the dark matters theory. Although this theory seeming can solve this problem, I think it is unlike to succeed. Also I found some doubts on this problem. Many years, physicists are finding the dark matters but still have no breakthrough. And physicists still can not found its possibilities and existence. I have some doubts on the dark matters theory: 1. If cosmos is occupied by the composition of dark matters, they may causing gravitational effects, they may be annexed by other heavenly bodies or self. But we have not found the sign. 2. If the cosmos is filling full of the dark matters, then we see the image (lights) from other heavenly bodies that should be distorted when they meet the dark matters. But we can see the clear and normal image. I think that maybe there is another solution can solve this problem that better than the dark matters. Therefore I am doubtful on the existence of dark matters.