Anti-freezing device of solar water heater

The invention belongs to the field of solar water heaters, and particularly discloses an anti-freezing device of a solar water heater. The anti-freezing device comprises a solar water heater main body, a water duct, fastening pieces, a heat preservation sleeve, a first valve and a second valve. According to the anti-freezing device, the heat preservation sleeve is wrapped around the water duct; anadhesion layer arranged on the inner side of the heat preservation sleeve is adhered to the water duct so as to improve the adhesion degree between the inner side of the heat preservation sleeve andthe water duct; connecting ends are inserted into outer grooves, and fixing blocks are further made to be inserted into inner grooves to fix the heat preservation sleeve, so that the connection stability of the two ends of the heat preservation sleeve is improved; a black nickel coating or a black chromium coating is coated on the outer side of the heat preservation sleeve and used for absorbing heat energy radiated by the