An automatic photoelectric detection system with high accuracy for laser alignment is discussed in this paper. The system consists of laser alignment, a photocell, a high precision displacement transducer, a motor -driven guide body, control circuit, and computer. Alignment laser, which is regarded as measuring datum, illuminates the photocell of detection system. The photocell is regarded as aimer. While the aimer is under aiming, a aiming signal controls a computer to acquire output data of the displacement transducer at that moment. The aimer is driven by motor-driver and passes aiming point in the two opposite directions in the process of measurement. The average value is used for measuring data. The measuring process is automatically accomplished by computer control. The distinguished feature of the photoelectric detection system is that the linearity error of photocell is elinimated, the range of measurement is enlarged, the sensitivity and accuracy is improved, and the measurement is completed automatically.