Abstract: In order to explore the theoretical process of high-precision ionospheric TEC inversion with tri-band beacon and analyze the influence of different observation errors on the inversion accuracy, this paper studies total electron content(TEC) inversion with tri-band beacon technology by simulating the Doppler frequency shift of satellite signal. Through the known satellite orbit coordinates, receiving station coordinates, satellite altitude angle and ionospheric background information, the Doppler frequency shift information in the signal propagation process is simulated using the signal propagation law, and the relative TEC is calculated; then, the phase integral constant is estimated by the multi-station method, and the dual-band beacon absolute TEC is calculated; then, the fractional part of Doppler phase shift is combined with the tri frequency phase integral constant to solve the high-precision tri-band beacon TEC. Comparing the inversion tri frequency TEC value with the prior background ionospheric TEC value, under the condition of 6° observation error, the relative TEC D-value means of tri-band beacon TEC inversion is within 4.5%, and the relative RMS is within 6%, the results show that tri-band beacon technology can effectively improve the inversion accuracy of TEC.