Signal-in-Space (SIS) accuracy is one of the basic performances of satellite navigation system.Considering the disadvantages of existing accuracy calculation models, we proposed a segmented SIS User Range Error (URE) evaluation model, carried out a study on the models for evaluation of SIS User Range Rate Error (URRE) and the User Range Acceleration Error (URAE), and used the broadcast ephemeris and precise ephemeris to evaluate the SIS accuracy of GPS and BDS. The results show that:the URE of BDS C02 and the URAE of GPS PRN10 are relatively larger, while the SIS URE, URRE and URAE of the other GPS and BDS satellites all conform to their own indicators.It verified the effectiveness of the proposed accuracy evaluation method.