The utility model relates to a five-prevention solar water heater composed of a water tank 1, a heat-insulation layer 2, a deflation-prevention tube 3, a single-direction valve 4 opened inward, an exhaust tube 5, a single-direction valve 6 opened outward, an overflow tube 7, a water supply and discharge water tube 8, a bracket 9, a glass tube 10, a pressure gauge 11, etc. The utility model has the characteristics of expansion prevention, deflation prevention, overflow prevention, wind prevention and snow prevention.