This paper presents a real-time system structure for high precision GPS measurement simulation. Firstly, the principle, function composing and appropriate mathematical models used in measurement simulation were studied. Secondly, according to different time constrains of different models' realization, a distributed simulation system was proposed to simulate GPS measurement. The system was divided into negative real time part, week real time part and strong real time part accordingly. Finally, an investigation experiment was made. The results showed that simulation system could satisfy the strong real time demand, and the simulated measurement reached a good degree of accuracy.