The method of preventing pipeline frost cracking is to use accompanying tropical zone at constant temperature. When the temperature of pipeline is lower than a certain value (e.g. 2 C), the accompanying tropical zone is heated by electricity, and when the temperature of pipeline reaches another value (e.g. 6 C), the accompanying tropical zone is cut off. The calculating method of the power of the accompanying tropical zone is: 8 mm wide, 15-20 watts per meter, up to 200 watts per 10 meters, using 0.5 square wire. If the width is more than 8 mm, the power per meter is more than 20 watts. The longer the tropical zone is, the greater the power will be; the constant temperature control circulating pump will make the water in the pipeline and the water in the tank exchange heat, increase the temperature of the pipeline and prevent ice. If the design of the automatic control cabinet is reasonable, the circulating pump for heat exchange between the collector and the water tank can serve as the anti-freezing circulating pump at the same time.