As we all know, the winter temperature in northern China is relatively low, and the duration of low temperature is longer, and the reaction tank of WWTP is generally set outdoors. Therefore, the low temperature in winter can lead to the decrease of biological activity and the weakened metabolism, resulting in unstable operation of wastewater treatment plant, deterioration. Affected by the geographical environment, the northern winter sewage temperature generally needs to be maintained at 5-10 ℃, then maintaining the water temperature is not less than 5 ℃ is the northern region of the sewage treatment plant is facing an important issue. In order to ensure that the reaction tank of the sewage treatment plant continues to run in the cold winter, the use of the principle of sunshine plate "insulation" has good effect on the antifreeze insulation of the sewage treatment plant's reaction tank.