Abstract: A system for detecting the parallelism of multi-channel optical axes was introduced, and a collimator was used in the system to provide an infinite target. Based on CCD image acquisition and processing and computer technique, the parallelism errors among the infrared axis, visible axis and the laser axis were calculated by calculating the pixels span in the CCD between the target cross center and the laser spot center. Result shows that the calculation error of the system is less than 5 .