Provided is a fuel supply system. The fuel supply system includes a fuel pump module mounted in a fuel tank and including a reservoir having a predetermined amount of fuel filled therein and a fuel pump mounted in the reservoir to suck the fuel filled in the reservoir and supply it to an internal combustion engine; a fuel supply line supplying fuel from the fuel pump module to the internal combustion engine; and a fuel return line returning the fuel from the internal combustion engine to the fuel tank, wherein the inside of the reservoir is provided with a bypass tube connecting the fuel return line to the fuel pump to directly supply the fuel returned through the fuel return line to the fuel pump through the bypass tube.