As is known to all, the temperature in north China is low in winter, and the low temperature lasts for a long time, while the reaction tank of sewage treatment plants is usually set outside. Therefore, the low temperature in winter will lead to decreased biological activity and weakened metabolism, resulting in unstable operation of sewage treatment plants and deteriorating water quality. Affected by geographical environment, the north winter water temperature generally need to be between 5-10 ℃, so, keep the water temperature is not lower than 5 ℃ is the important problem facing north sewage treatment plant. In order to ensure the continuous operation of the reaction tank of the sewage treatment plant in the cold winter, the anti-freeze and thermal insulation measures of the reaction tank of the sewage treatment plant have a good effect by using the principle of "heat preservation" of the polycarbonate hollow sheets.