Accurate estimation of vehicle state variables and uncertain parameters can improve the robustness of vehicle dynamic control system. The concept of uncertain vehicle parameter-set was proposed. The state space model for the estimation system was established. The estimation of the state variables and uncertain parameter-set were completed based on the UKF theory. The comparison with the reference model showed that the estimation method was effective and could get the precise results. A transformed magic formula tire model was also proposed to calculate the cornering force in the estimation process. The tire model reduced the parameters and could realize the precise estimation of tire lateral force. 