This thesis presents the concept of on-line measurement on weld beads in grinding process and analyze the measurement results using graphical method. Among three measuring methods including the machine vision, the coordinate measuring machine and the contact-type deflection sensor, the use of the contact-type deflection sensor is most suitable for weld beads in grinding process. There are three major steps in the grinding experiment. First, read the data from the detection path of the robot arm; second, plot the data with respect to the time; finally, determine the detection standard of grinding surface and analyze the flatness of the grinding workpiece. According to the concept of Industry 4.0, the efficiency and precision of the grinding process could be improved by collecting and analyzing the big data of the grinding system. In this study, the surface measurement system consisted of an ABB IRB 120 robotic arm and a METROL Sensor. The algorithms of path planning and graphical analysis were performed using the ABB's RobotStudio and MATLAB software, respectively. In the case of static workpiece, an on-line measurement procedure was carried out in this study to determine the flatness without reloading the tools.