In order to address the deficiency of vehicle plane stability region, according to the nonlinear vehicle dynamic model, a method of estimating vehicle spatial stability region was proposed.A 3DOF bus model with Pacejka Magic Formula tire model was deduced and verified by comparing vehicle tests.Based on the Jacobian matrix of the dynamic system, the stability of the vehicle system was discussed with Hurwitz criterion.In addition, by establishing a generalized function for bus system, the full loaded vehicle’s spatial stability region in 20 m/s was given on the basis of Lyapunov theory and vehicle system characteristics.A vehicle test in the same condition has shown that the calculated stability region defined by Lyapunov and system stability theorem has a good effect on characterized vehicle stability.It will be a valuable reference for vehicle stability evaluation and control.