The existing of transmission line icing may lead to the collapse of the transmission tower and disconnection of the transmission line,which seriously threatens the safe and stable operation of power grid. In this paper,aiming at the typical icing lines in Guizhou,the simulation model of 500 kV tower-line system is established by finite element simulation method,and the simulation analysis of different icing thicknesses and different wind speeds under uniform icing is carried out. The weak point position rules of 500 kV transmission tower are obtained by counting 25 groups of simulation results. Then,based on the axial stress and node displacement of the weak components of the transmission tower, the operational risk assessment analysis of the transmission tower is carried out,and the operational risk state of the transmission tower is divided. Furthermore,the effect analysis of two kinds of reinforcement measures is carried out,and the relationship between axial stress and node displacement at different weak points of the transmission tower before and after reinforcement is obtained. The results show that the weak points of the 500 kV transmission tower are mainly distributed at the ground bracket of the tower head,the joint of the upper and lower curved arms, the bottle neck and the body of the tower. Under uniform icing and wind load,the axial stress and node displacement of key components increase nonlinearly. The critical expressions of safety,warning and dangerous state of the transmission tower are fitted. The reinforcing effect of increasing the cross-sectional area of components is better than that of changing the angle steel structure with weak points. The axial stress and joint displacement of the transmission tower at the weak point have no obvious change before and after reinforcement when changing the angle steel.