The invention relates to an immersion heater and a control method thereof. The immersion heater comprises a heating element, a protective sleeve sleeved on the outside of the heating element, a bracket arranged inside the protective sleeve and used for supporting and fixing the heating element, and a terminal connected with the heating element. The heating element comprises a top cold end section,an intermediate heating section and a bottom cold end section, wherein the top cold end section extends out of the nozzle of the protective sleeve and is connected with the terminal, and the bottom cold end section is connected with the bracket. The immersion heater of the invention not only satisfies the heating function, but also has reasonable temperature distribution of the heating element, is not easy to burn out the wiring terminals, is not easy to loosen after the internal element is fixed by the bracket, has high stability and long service life.