The lunar probe requires accurate information on position and velocity when it runs on its close phase of orbit. Dynamical estimation with GPS can provide the accuracy needed. This paper presents a description of the conditions about choosing the GPS satellites and the numbers of the available GPS satellites on close phase of orbit, the solutions of dynamical method with GPS, and the influences with different sampling intervals and force models. The results show that the dynamical method with GPS can meet the precision requirement with reduced force models and 5s sampling interval.