A 7 degree-of-freedom (DOF) 4 wheels vehicle dynamics model based on Matlab-Simulink is established, and 7 DOF vehicle dynamics equations in the form of nonlinear state-space standards are given. The characters of the electronic throttle and the active braking system have been analyzed. And the electronic throttle model and the active braking system model are built according to the test results respectively. Off-line simulation results indicate that the model is suitable for the vehicle adaptive cruise control system, and both of the electronic throttle and the active braking system work in a reasonable way. An adaptive cruise control (ACC) example illustrates that the model has a good performance in cruise and distance keeping.