The faucet's quality inspection is an integral component of the faucet production process. Sensitivity is an essential parameter to be considered in the detection process. In the traditional sensitivity measurement method, the angle of the rotating handle is reflected by the angle of the motor rotation. However, the motor's axis and the faucet's axis are not the same, so the angle measured by the motor is not the angle of the handle. There is a large error through the mechanical transmission structure to drive the handle movement, no matter the adopted transmission method. This article proposes a faucet rotation angle detection system that uses machine vision to measure the faucet handle's rotation angle. Experiments show that the system's measurement error is less than ±0.5° and meets the system's error requirements for the rotation angle of the faucet handle when the camera's installation height is within a specific range.