The utility model discloses a four-blade differential pump driven by sinusoidal non-circular gears. The power of the differential pump is output by a motor and then delivered to an input shaft via a coupler; the first sinusoidal non-circular gear and the second sinusoidal non-circular gear are fixed on the input shaft; the first conjugated sinusoidal non-circular gear is fixed on an output shaft, and engaged with the first sinusoidal non-circular gear; the second conjugated sinusoidal non-circular gear is fixedly connected with a second impeller via a shaft sleeve; the shaft sleeve is movably sleeved on the output shaft; the second conjugated sinusoidal non-circular gear is engaged with the second sinusoidal non-circular gear; a first impeller is fixed on the output shaft; each of the first impeller and the second impeller is provided with two blades; a one-way pressure release valve is mounted in each blade; and directions of the one-way pressure release valves are consistent with rotation directions of the blades. The differential pump is high in displacement, stable in flow and easy in non-uniform speed rule adjustment, and effectively solves the problems of pressure pulsation and fluid trapping of the traditional differential pump.