With the expansion of power grid scale, the 110 kV power grid is most used as the high-voltage distribution network in mega cities. The reliability of double chain connection and "3T" connection of two typical connections in a 110 kV high-voltage distribution network is compared. The method of solving the reliability index of two typical but different connections by analytic method and the theoretical calculation value are given. In addition, the sensitivity analysis of two different wirings is also carried out. The results show that the two connection modes can meet the needs of actual operation of a power grid structure, but the outage time of "3T" connection is shorter than that of a double chain connection, and the sensitivity to the correct operational rate of the standby automatic switching device is better. This work is supported by the Natural Science Foundation of Guangdong Province (No. 2017A030313304).