A valve has a valve body, a valve member, a bonnet, an anti-loosening stem and multiple fillers. The valve member is mounted inside the valve body, and has a first mounting part and a groove that is defined annually in the first mounting part. The anti-loosening stem is mounted through the valve body, and has multiple embedding elements and a second mounting part that is mounted in the first mounting part. The embedding elements are mounted radially in the anti-loosening stem and abut the groove. Thus, the anti-loosening stem is mounted firmly in the valve member. The bonnet abuts the fillers and is mounted in the valve body. Therefore, the anti-loosening stem is prevented from detaching or jetting out of the valve member and damaging the user when removing the bonnet to replace the fillers.