Aiming at a car modified as SUV, the layout of the front Macpherson steering suspension system needs to be redesigned after raising the car body. As a result, the toe-in of front wheel changes towards a positive rate in the process of the wheel jounce, which causes the vehicle tends to over steer. And Ackerman deviation is large which makes severe tire wear in progress of turning around. According to the structure characteristics of Macpherson suspension mechanism, the kinematics of suspension is analyzed based on space geometry method when it has or not has the steering linkage. And the influences on the amount of toe-in and camber of steering linkage are found. The optimization model is set up based on the influences on toe-in of steering linkage and space limitation of splitting point, which is calculated with Matlab. After optimization, the toe-in deterioration is eliminated, and Ackerman deviation is effectively reduced. As a result, the handling and stability of the vehicle and tire wear are improved in progress of turning around.