In order to avoid damage avalanche photodiode(APD)during the the receiver and transmitter axis testing process of ZY-satellite laser altimeter, a new test method suitable for vacuum environment was proposed. The test system was established through the collimator and laser beam analyzer, and the optical cable connector was sealed through the cabin, a 1064nm continuous light source outside the tank was connected to a designed fiber-optic homogenizer, which was fixed on the focal plane of receiver to produce a uniformly illumination beam and get the optical axis of the receiver. The optical axis of the transmitter was got by multi-stage attenuation. The results show that the method eliminates the risk of APD damage in vacuum environment, and the measure accuracy is better than 6.47μrad, which meets the requirements of laser altimeter. The method has the advantages of compact structure and high precision. It provided a new idea for vacuum test of high energy laser rangefinder and has a wide application prospects.