Fractional heater

The embodiment of the utility model provides a fraction heater, and relates to the technical field of fraction heating. The fraction heater comprises a heat insulation cover, a heating disc is installed in the heat insulation cover, a solution device is placed in the heating disc, a preheating assembly is installed on the upper side of the heating disc and wraps the solution device, the upper end of the heat insulation cover is rotationally connected with a sealing assembly, and the sealing assembly is used for sealing the upper side of the preheating assembly. The bottom of the solution device is heated through the heating disc, the second preheating sleeve slides upwards to drive the outer sleeve and the inner sleeve to slide upwards, the outer sleeve and the inner sleeve drive the first preheating sleeve to move upwards together, and the first preheating sleeve, the inner sleeve and the second preheating sleeve wrap the solution device. And the heating pipe generates heat to preheat the solution device fro