The vehicle roll behavior with steering input is an important part of driving safety,and finding the vehicle dynamics ac-curately in a real driving scenario is a serious concern.However,previous research has seldom considered the relation between road exci-tation and vehicle lateral response with steering input.To address this issue,a comprehensive analysis of vehicle roll behavior with steer-ing input is studied in this paper.Based on the power spectral density(PSD)definition of road roughness and its relationship,a three-dimensional(3-D)road surface model is first introduced for international standardization organization(ISO)level A and level C type road excitations.Then,a 6 degree of freedom(6-DOF)model including vertical and lateral dynamics is proposed.By varying the vehi-cle parameters,such as vehicle total mass,track width and the height of the center of gravity(C.G.)of sprung mass,the system re-sponse relationships between road excitation and rollover index(RI)are illustrated.The simulation results show that,1)the influence of the height of C.G.due to vehicle mass transferring on roll behavior is most sensitive under constant road excitation,2)a positive re-lationship between road excitation level and roll response can be found under constant vehicle parameters.Finally,the proposed model is validated in CARSIM(R)software and the simulation results confirm the accuracy of the model.It is also found that the height of C.G.due to vehicle mass transferring and road excitation level cannot be ignored whilst analyzing the vehicle roll behaviors with steering input.The research achievements provide a theoretical insight to improve the rollover theory and will have significant contribution to practical appli-cations.