Abstract: Satellite-to-satellite tracking can provide a new technique for the earth gravity field determination.To discover the relationship between the earth gravity field and SST observation,the basic research of SST simulation,JGM-3 and EGM96 are adopted and some numerical simulations are put in practice.The variations of SST observation are compared with the different degree and order and two earth gravity models JGM-3(8×8,36×36,50×50,70×70) and EGM96(70×70,100×100,150×150,180×180,200×200,250×250,300×300,360×360).In these simulation results,the higher degree and order earth gravity model can provide better simulation results.At the same time,the results simulated by the two different models have obvious biases.