In order to improve the positioning accuracy of micro-positioning stage,an experimental method is presented to calculate the coupled inputs of a planar 3-DOF micro-positioning stage, which is based on the micro vision. To measure and record the input distance of stage by the micro vision system, a calibration is made between the stage coordinate system and the image coordinate system. All of these are useful for the improvements of coupled inputs precision. Finally, the results of experiment show that, this method has many advantages such as small amount of calculation and high precision of measurement. Besides, it has an important meaning to analyze the structure of micro-positioning stage.