In response to the demand for suppressing laser intensity noise in the millihertz frequency band in space gravitational wave detection, based on a low-noise chip and combined with a high stability voltage reference source, this paper designs relevant peripheral circuits to carry out the overall design and development of a semiconductor laser pump driver in a spaceborne laser amplifier. The performance of the pump driver is evaluated from both the time and frequency domains. Experimental results show that when the self-developed pump driver outputs 3.5 A, the current time-domain jitter is ≤180 μA within 4 h. In the frequency domain, by converting the current signal into a voltage signal through a sampling resistor, the voltage noise spectral density is less than 1×10^-4 V/Hz^1/2 at 0.1 mHz and 1×10^-5 V/Hz^1/2 at 1 mHz. The developed pump driver outputs laser intensity noise with a relative voltage noise spectral density below 1×10^-3 Hz^-1/2 at (0.1 mHz?1 Hz) in the frequency range of space gravitational wave detection. This study provides key components and experimental basis for laser intensity noise suppression in space gravitational wave detection.