A precision analysis method of four-satellite Time Difference Of Arrival(TDOA) location based on Geometric Dilution Of Precision(GDOP) is proposed. Firstly, the 3D location precision model based on TDOA is investigated. Then, the influences of the time measurement error and location error on the above precision model are analyzed. Finally, the GDOP of representative four-Satellite of Y, T, square and anomaly are simulated. The influences of the length of baseline, the satellite and target altitude on location precision are analyzed. The simulation results show that four-satellite location of Y distribution based on TDOA achieves the best precision. The increase in the length of baseline and satellite altitude contributes to improving the precision of location.