At present, the calibration of water meters in China mostly adopts manual calibration, and there are many repetitive manual operations in the process, which makes the calibration process time-consuming and laborious. In order to solve this problem, robots were used to replace the manual work to complete the calibration in the process of water meter calibration and a water meter grasping method based on machine vision was proposed in this study. Different types of water meters in different environments can be detected through the YOLOv3 network in the system. After obtaining the type and position of the target water meter, the system carries on the dection of position and posture of the water meter to obtain the coordinates of the grasping point and the attitude angle of the water meter, and controls the robot to grasp the water meter. Experimental results show that different types of water meter in different external environments can be grasped and accurately placed with the system, the system has sound robustness and high grasping success rate, and can satisfy the needs of actual water meter automatic calibration line.