The invention provides an AC looped network power supply dynamic acceleration overcurrent protection method and a protection device. The protection method comprises the following steps: when a local side protection device receives a CT disconnection signal of an opposite side protection device and dynamic acceleration overcurrent protection meets a starting condition, a circuit breaker corresponding to the local side protection device is controlled to act and trip in a dynamic acceleration overcurrent protection T2 time limit; when the local side protection device does not receive the oppositeside overcurrent starting signal and the opposite side CT disconnection signal, the communication channel between the local side protection device and the opposite side protection device is normal and the dynamic acceleration overcurrent protection meets the starting condition, a circuit breaker corresponding to the local side protection device is controlled to act and trip in the dynamic acceleration overcurrent protection T1 time limit, wherein T2 is greater than T1, and T1 is the action delay time of dynamic acceleration overcurrent protection when the local side protection device operatesnormally. By means of the protection method, the situation that the fault removal range is too large can be avoided, and the reliability of AC looped network power supply is improved.