To investigate the seismic reliability of transmission towers under the influence of Soil Structure Interactions （SSI） and tower-line coupling effect， a seismic reliability analysis method of transmission tower-line coupling system considering the SSI effect was proposed. Firstly， a simplified mechanical model of the transmission tower-line coupling system considering the SSI effect was developed， and the dynamic equation under stochastic seismic excitation was derived. Secondly， the random function-spectrum representation model was used to generate random seismic acceleration time-history samples， and the seismic dynamic response of the coupling system was analyzed. Thirdly， the maximum entropy and fractional moments based on GF-discrepancy points were used to predict the distribution function of the extreme-value variable of random seismic response， and the coupling system’s seismic reliability was solved. Finally， the effectiveness of the proposed method was verified through a transmission tower-line system from an actual project. The results show that： When the foundation soil category is type Ⅳ， after considering the SSI effect， the maximum vertex displacement and acceleration increase by 46.59% and 17.43%， respectively， and the failure probability increases by 70.32%. When considering the tower-line coupling effect， the maximum vertex displacement is reduced by 0.51%， the maximum vertex acceleration increases by 1.74%， and the failure probability is reduced by 15.71%； For the transmission tower-line coupling system considering the SSI effect， the foundation soil becomes softer， and the maximum vertex displacement and acceleration become larger. Compared with results using Monte Carlo Simulation （MCS）， the maximum relative error of the proposed method is 9.97%. The proposed method has high accuracy and efficiency.