Many doll friends may encounter a problem when using sex dolls. The penis is easily extruded by the strong thrust of the vagina. Sex dolls usually have narrow vaginal passages. When something enters the channel (silica gel or TPE), there is a reverse thrust at the end of it. This pushback does not exist in human sexual activity except during orgasm. Because the structure of the female vagina is soft, there is no strong direct resistance. This problem leads to a decrease in the experience during use, and the reverse thrust of the front end greatly stimulates sensitive parts of the human body, causing the game to end prematurely and unable to enjoy a longer period of comfort. We test some methods to solve this problem. Design and testing took 3 months. We got the final solution. It balances cost and performance well.