A photoelectric detector spectral response test system and a measurement method thereof belong to optical radiation calibration measuring instruments and methods, and solves problems of expensive cost and difficulty in guaranteeing measurement precision of existing test systems to realize high precision measurement of spectral response. The test system of the present invention comprises a sinusoidal modulation light source, a condensing lens, a monochromator, an optical filter wheel, a camera obscura, a motor-drive circuit, a microcontroller control circuit, a preamplifier circuit, a sine phase lock amplification circuit, a data collection card and a computer. The sinusoidal modulation light source is a sine-modulated incandescent lamp, a halogen tungsten lamp and an LED light source. According to the invention, a programmable device is employed to realize a mode of sine phase lock amplification, and photoelectric detector spectral responses in a scope of 300-900nm is measure and drawn. While high-precision measurement is realized, the equipment cost and design difficulty are also reduced.