Abstract: The spectral relationship between range-rate error and gravity potential error for SST-ll is established based on energy conservation theory,the performances of satellite separation,altitude of orbit,and precision of range-rate in recovering the earth's gravity field are analyzed.The simulation results indicate that increasing the separation of satellite pair can improve the accuracy of low degrees of geopotential.When the separation is more than 500 km,it is no longer helpful for improving the accuracy of geopotential.The lower altitude of the orbit is good for obtaining higher accuracy of the high degrees of geopotential.When the obrbit reduces 100 km,the maximum degree increases more than 20 degrees.Higher precision of range-rate is very important for recovering the earth's gravity field,when the precision is improved an order of magnitude,the maximum degree increases about 28 degrees.Comparing to the models of GGM02S and EIGEN-GRACE02S,it basically reflects the performance of GRACE and proves the feasibility of this method.