A fixture for radial micromotion experiment is disclosed. Its experimental method is to control load or control deformation. The fixed upper test part and the lower test part moving along with the piston driven by a high-precision hydraulic servo system are contacted in sphere/plane contact mode. The load signal is measured by a load sensor above the upper test part. The relative deformation between test parts is measured by high-precision displacement sensor. They are then input to computer for processing.