The invention provides a protection unit of a prepayment device. The structure of the protection unit comprises a voltage transformer, a voltage collection module, a current transformer, a current collection module, a prepayment ammeter, a memory, a CPU (central processing unit), a switching power supply, a prepayment device vacuum switch and a signal drive circuit, wherein the voltage transformer is connected with the CPU through the voltage collection module; and the current transformer is connected with the CPU through the current collection module; and the prepayment ammeter, the memory, the switching power supply, the prepayment device vacuum switch and the signal drive circuit are respectively connected with the CPU. According to the invention, the integrated protection unit of the prepayment device is designed by using elements of the prepayment device, comprising the transformers and a circuit breaker and the like, and has the functions of short-circuit protection, overcurrent protection, zero sequence overcurrent protection, wireless communications and the like, so that the prepayment device has protection function. In addition, by using the protection unit of the prepayment device provided by the invention, while the investment of prepayment clients is reduced, the function of protecting the equipment of the clients can be realized, and the reliability of power supply is also improved at the same time.