We illustrate the principle of Digital satellite TV differential timing (DSTVDT) and propose an optimal weighting method that reduces the timing error introduced by satellite ephemeris error.A mathematical formula for the timing error introduced by satellite ephemeris error is derived and analyzed.On the basis of the derived formula,the proposed optimal weighting method based on multi-base stations is presented.The results of data simulation and experiments show that when the proposed method is applied,for a satellite ephemeris error of 10km,the ephemeris-introduced timing error is less than 10ns,which is important for improving accuracy and stability of the timing system.