The invention provides a power redundancy method for an electronic control system. The control system comprises a plug-in, a power switching circuit, a power detecting circuit, a first load, a secondload, a micro control module and a power module. The states of multi-way input power sources in the electronic control system with a multi-way input power source are detected, an input power source ofan internal circuit is actively switched, and it is ensured that when input of one way power source of the system loses efficacy, the complete power input can still be obtained.