The invention provides a brake assembly with a corner type brake shoe friction plate abrasion alarm device. The brake assembly comprises a brake bottom plate, a cam shaft, an active brake shoe iron belt friction plate assembly, a driven brake shoe iron belt friction plate assembly, a cam support, a spring brake cylinder, an automatic adjusting arm, a brake friction plate abrasion alarm sensor andother parts. According to the brake assembly, the brake friction plate abrasion alarm sensor is used for detecting the adjustment angle difference value between the automatic adjusting arm and the camshaft to judge whether the brake shoe friction plate reaches the abrasion limit, a corner displacement signal is converted into an electric signal, and then the electric signal is converted into a sound, light and other signals to give an alarm to a driver in the driving room. According to the brake assembly, the brake assembly body does not need to be changed, only the cam shaft needs to be correspondingly changed, the abrasion limit of the brake shoe friction plate can be monitored, the brake friction plate abrasion alarm sensor can be repeatedly used, and the service life is long.