Taking the external thermal insulation method of plastered polystyrene board without anchor bolt， plastered polystyrene board with steel anchor bolt and polystyrene board with inserted steel wire mesh as the calculation cases， the temperature field of the external thermal insulation wall was calculated. According to the temperature field， the normal displacement of the wall with different external insulation methods under the condition of high and low temperature was calculated by finite element method， and the influence of different external insulation methods on the safety performance of the structure was analyzed. The results show that the normal displacement of external wall insulation system presents expansion in summer and contraction in winter， and the primarily normal displacement source is the insulation layer. The normal displacement of each functional layer of the external insulation system wall can be significantly reduced， and the stability and safety of the external insulation system can be improved as the result of setting steel anchor bolt， steel wire mesh and other reinforcement components. The maximum normal displacement of the surface layer by the polystyrene board with inserted steel wire mesh is smaller than the plastered polystyrene board with and without anchor bolt.