A gradient liquid feed pump system capable of liquid feed in a correct mixing ratio even in the case of liquid feed in which the mixing ratio varies. Specifically, it comprises a first plunger pump for sucking and delivering an eluate, a second the first and second plunger pumps through a cam, a first pressure sensor for measuring the pressure in the flow path of the second plunger pump, a second pressure sensor for measuring the pressure in the fist plunger pump, a cam position detecting sensor for detecting the cam position, wherein when the cam position is in a delivery interval, the rotary speed of the motor is increased, and the period for decreasing the rotary speed is determined on the basis of the difference between the pressure values obtained from the first and second pressure sensors, respectively. Thereby, liquid feed can be smoothly effected with correct mixing ratio while avoiding pressure interference between pumps.