This　paper　presents　a　novel　experimental　approach　and　a　simple　model　for　verifying　that　spherical　mirror　of　laser　tracking　system　could　lessen　the　effect　of　rotation　errors　of　gimbal　mount　axes　based　on　relative　motion　thinking.　Enough　material　and　evidence　are　provided　to　support　that　this　simple　model　could　replace　complex　optical　system　in　laser　tracking　system.　This　experimental　approach　and　model　interchange　the　kinematic　relationship　between　spherical　mirror　and　gimbal　mount　axes　in　laser　tracking　system.　Being　fixed　stably,　gimbal　mount　axes＇　rotation　error　motions　are　replaced　by　spatial　micro-displacements　of　spherical　mirror.　These　motions　are　simulated　by　driving　spherical　mirror　along　the　optical　axis　and　vertical　direction　with　the　use　of　precision　positioning　platform.　The　effect　on　the　laser　ranging　measurement　accuracy　of　displacement　caused　by　the　rotation　errors　of　gimbal　mount　axes　could　be　recorded　according　to　the　outcome　of　laser　interferometer.　The　experimental　results　show　that　laser　ranging　measurement　error　caused　by　the　rotation　errors　is　less　than　0.1　mu　m　if　radial　error　motion　and　axial　error　motion　are　under　10　mu　m.　The　method　based　on　relative　motion　thinking　not　only　simplifies　the　experimental　procedure　but　also　achieves　that　spherical　mirror　owns　the　ability　to　reduce　the　effect　of　rotation　errors　of　gimbal　mount　axes　in　laser　tracking　system.