Abstract: The gravitational reference sensor is a key load in the space gravitational wave detection and other missions. The charge accumulation in the test mass is coupled with the surrounding electric field and magnetic field in several of cosmic environments. The interference generated will affect scientific objectives. This paper studies the charge control of the 255 nm ultraviolet(UV)LED on the test mass,and controls the discharge rate of the test mass between 0~10 pA. The DC charge control experiment studies the effect of light intensity,incident angle,pressure,and bias on the photoelectric response. The AC charge control experiment controls the discharge rate of the test mass by adjusting the phase of the light source drive and bias voltage,and controls the discharge rate between -3~+3 pA.