The invention relates to the technical field of internal combustion engines and discloses a fuel system and a control method thereof. The fuel system comprises an oil tank, a heater, a fuel pump and an oil spraying nozzle, wherein the heater is installed in the oil tank, the fuel pump communicates with the oil tank through a first oil inlet pipeline, the oil spraying nozzle communicates with the fuel pump through a second oil inlet pipeline, and the oil spraying nozzle communicates with the oil tank through a first oil returning pipeline. According to the fuel system and the control method thereof in the embodiment of the invention, the rest of high-temperature fuel burned by the oil spraying nozzle flows back into the first oil inlet pipeline or the oil tank, the high-temperature fuel is mixed with low-temperature fuel in the first oil inlet pipeline or the oil tank and then conveyed by elements such as the fuel pump into the oil spraying nozzle to be burned again, thus damage of the high temperature to the fuel pump and other elements can be reduced to a great extent, and the service life is prolonged; meanwhile, the temperature of the fuel at the oil inlet end can be increased, the consumed time of fuel preheating is shortened, energy consumption of the fuel heater is reduced, and the cost is lowered.