The x ray collimator mainly controls the opening of the X-ray and the size of the light field and the direction of the X-ray. Therefore, the quality problem of the x ray collimator is a very important issue. But how to judge the quality of the beam limiter? When we receive the beam limiter we purchased, we should first check whether the lead leaf blade of the x ray collimator can be closed. If the lead leaf is not closed, the X-ray will leak out and surround it. Radiation from things, especially those who work in the radiology room, will pose a huge threat to their health. Therefore, we have to choose the x ray collimator that the lead leaf can be closed. Then we need to look at the lens in the x ray collimator. Whether there is dirt on it, which affects the emission and refraction of X-ray, directly affects the quality and dose of X-ray. Therefore, it is important to know the quality of the test x ray collimator.