The propagation of laser beam for intersatellite laser communications belongs to the farfield diffraction, but the optical testing and verification in the laboratory is on the condition of the nearfield diffraction. In terms of the Fresnel diffraction theory, the inherent difference on the optical tracking position errors between the farfield and nearfield effects is studied, their equivalent conditions are analyzed. And it is found that the use of beam scanning in the nearfield testing can accurataly simulate the mutual movement of satellites in the farfield and the trajectory formula for beam scanning is deduced. Investigation on the characteristics of focused spot and the effect from satellite vibration is presented. The results clarify the basic concepts necessary for the testing of optical tracking performance of intersatellite laser communication terminals, which would provide helps in the ground testing.