In recent years, intelligent vehicles have become one of the major research topics in vehicle engineering and created a new opportunity for the automotive industry. Simulation and real experiment are both essential to the development of intelligent vehicle technologies. Vehicle positioning system, such as GPS (global positioning system), plays an important role in intelligent vehicle development. The GPS model plays important role in the development of intelligent vehicle simulation system. Primarily focusing on application requirements of intelligent vehicle simulation platform for GPS sensor modeling, with considering the major factors affecting the positioning accuracy in vehicle driving environment, this paper establishes a new GPS model and algorithm based on physical and functional characteristics of GPS. As the basis of this model system, a precise ephemeris model is established to obtain the coordinates of GPS satellites at any given time. A new occlusion model is proposed in order to describe the external environmental disturbance more effectively. This model takes into account not only the emission angle of the satellite signal and the shadow of the earth, but also the blocking from scene objects, such as buildings, trees and other shelter. By using the Doppler effect and solving the pseudo range equation, velocity and position are calculated. And in the process of measurement, the pseudo range error and the frequency shift error are taken into account. The proposed GPS model has good fitting precision and the performance of the entire system is verified through comparing with the measurement data from real GPS sensor.