The location accuracy of Dual-Satellite Geolocation system, that estimates the location of a stationary source using Difference Time Offset (DTO) and Difference Frequency Offset (DFO) measurements of a signal as retransmitted by the two adjacent geostationary satellites and received by two ground stations in the area of visibility of both satellites, is relevant to the accuracy of parameters estimation and ephemerides of two satellites. With the analysis of the location principles and parameters measurements, the constrained CRLB of the location accuracy has been derived in this paper. Simulation results verify the theoretical development.