High precision of GPS/LEO Radio Occultation (RO) technique in atmospheric profile retrievals is achieved. There are a few of GPS/LEO RO projects abroad at present, but related in-depth experiment had not been done in China, which restricted the development of domestic RO technique greatly. Research method of GPS/LEO radio occultation based on Satellite Tool Kit (STK) is presented, and then condition of RO occurrence and formula of calculating position of tangent point are addressed according to principle of GPS/LEO radio occultation. With the criterion process of RO having been simulated by STK, the occultation data is obtained. Index of atmosphere refractivity is gained by inversion according to known atmosphere model based on the assumption of the spherical symmetric atmosphere. It indicated a better precision of inversion data through the comparison between atmosphere model and inversion data, and the feasibility of simulation of GPS/LEO RO experiment by STK is validated.