Abstract: An on-line robot measurement and machining system is constructed thanks to the application of robot scanning system in industrial machining.By using a sphere with known diameter as calibration object， a new online approach based on nonlinear least squares optimization with geometry constraints is proposed to calibrate the pose of the portable scanner relative to the robot.Meanwhile，a new approach is also proposed to increase the machining accuracy by using virtual knife tool center point （TCP） together with a technique of robot system error pre-compensation.The experiment of scanning and machining the edge of a guitar is given to demonstrate the good stability，high precision，and high degree of automatization of our system.