The invention discloses a vapor-liquid phase separation type gravity heat pipe solar boiler, which comprises a water pump, a first bracket, a drum, a metal flexible pipe, a heat pipe type solar evaporator, a bucket, a condenser, a controlling valve, a one way valve and a solar optical collector; the upper end of the first bracket is provided with the drum which is connected with the heat pipe type solar evaporator by the metal flexible pipe so as to form the vapor-liquid phase separation type gravity heat pipe, the drum is connected with the condenser by the one way valve through the controlling valve, the water pump is connected with the drum, and the position corresponding to the heat pipe type solar evaporator is provided with the solar optical collector which is driven by a hydraulic device for tracking the sun. The solar boiler adopts the solar optical collector for focusing the sunlight to the evaporation section of a loop type heat pipe so as to generate heat and adopts the characteristic of high-efficiency heat transmission of the loop type gravity heat pipe for transmitting the heat into the boiler so as to carry out heat exchange with the water in the boiler and generate medium and high temperature saturated vapor; and the boiler has high system efficiency, is not easy for scale formation, is simple and can operate with high efficiency for a long time.