A method based on interpolating sampling technology is proposed in this paper to achieve high precision time difference measurement in TDOA location system. Compared with traditional methods, this method converts the clock quantization error’s measurement to the phase measurement of reference signals, thus completely eliminating the traditional methods’ principle error. Theoretical analysis and MATLAB simulation are discoursed fully in the paper. Results show that a time difference measure precision within 70 ps can be achieved under the current device performance. This technology can also be used for the clock synchronization of base stations in TDOA location system. And the clock synchronization error will be effectively reduced. So the positioning accuracy shall be further improved as well.