In order to achieve high-precision observations of solar spectral irradiance, a method which combines solar motion trajectory tracking and four-quadrant detector based on photoelectric tracking was adopted. The principles of solar motion trajectory tracking and the design of the tracking device based on four-quadrant detector were discussed in detail. To test the tracking precision of the device, a test system based on linear CCD was designed, and the outdoor experiment was carried out. The results show that the sun-tracking accuracy of the device is better than ±0.030, and the stability is better than 1.4%, which meet the requirements of the high precision spectral irradiance observation.