A fuel supplying system of an LPI engine is capable of improving performance of a fuel pump by decreasing suction pressure thereof. A fuel supplying system of an LPI engine may include a fuel tank storing fuel, a fuel pump feeding fuel supplied by the fuel tank to the engine through a fuel supplying line, and a fuel return line for returning fuel from the engine to the inside of the fuel tank. The fuel pump may be divided into a pump chamber and an operating chamber, and a vent hole is formed at a case of the fuel pump.