Underwater alarm bracelet and working method thereof, as well as underwater alarm system

The invention relates to an underwater alarm bracelet and a working method thereof, as well as an underwater alarm system. The underwater alarm bracelet comprises a pressure sensor used for measuring underwater pressure and a processor module connected with the pressure sensor, wherein the processor module is further connected with a clock chip and an alarm module; and the processor module is suitable for judging underwater conditions of a human body according to data of the pressure sensor and underwater retention time data, and controlling the alarm module to alarm. The underwater alarm bracelet, the working method thereof, and the underwater alarm system can effectively monitor state of underwater acting personnel, judge physical index of the personnel, evaluate the body condition in time accurately, make corresponding emergency responses, and greatly guarantee personal safety of people in swimming, diving and the like activities.