A method is proposed to research and test the process parameters for automatic car paint sanding and polishing process.A robot system for automatic sanding and polishing system is introduced to the finishing line of car paint workshop,in which the process control is realized through the control of sanding/polishing tool system by robot programs.The test procedure is divided into two phases:material test in lab and continuous test on production line.The parameters including pressure force on surface,rotation speed of the tool and feedrate of the robot are controlled in the tests and the quality results are evaluated by the finished surface roughness and paint layer thickness.The test results demonstrate that this method can realize the construction of process database for car paint defect automatic repair process.