In order to study the failures of transmission line caused by overheating of hard tube bus，a large current test is designed． The main factors which affect the overheating of hard tube bus are the contact pressure and the passing current through changing the moment of the bolt torque and the size of the tube current． Based on the analysis of the influencing factors，the measures to reduce the roughness of the contact surface and increase the heat flux of the material are put forward to improve the heating condition of hard tube bus． Finally，the effectiveness of the proposed measures is verified by an effective simulation model．