In this study, the auxiliary wheels that can assist roll of the scooters can make the disabled people have more safety choices in the transportation. According to the existed design of non-assisted roll auxiliary wheel as a reference, we measured the fixed position of the auxiliary mechanism, and plan the space of the mechanism design, calculate the degree of freedom, and the size synthesis can be carried out. Finally, we simulate the handling test for verification. The results show that the auxiliary wheel designed in this study can have better sensitivity from low speed to high speed in each route, and can withstand extremely high lateral acceleration at high speed with high resisting overturnability.