A cquisition, pointing, and tracking is an important component in space laser communication. It is the premise and guarantee to normal work. Line-of-sight initial alignment is researched in detail and initial alignment model is proposed. Coordinate conversion method is used to solve alignment affect to azimuth and pitch angle, by compensating position change, attitude varying, difference to installation datum, initial zero inconsistent. Calibration method on initial alignment line-of-sight is proposed. Acquisition uncertain area and alignment accuracy are determined according to error theory. In dynamic aircraft to aircraft, the initial alignment performance is tested by using the parameters of position, attitude provided by double antenna global position system/inertial narigation system (GPS/INS). Area of uncertainty measured by observation camera is 10 mrad and it is consistent with theoretical analysis results.