DC protection method by using analog AC rectification in DC supply system

The invention discloses a DC protection method by using analog AC rectification in a DC supply system, which is characterized by comprising the following steps: 1) accessing AC electric quantity of a rectifier transformer connected with a rectifying device to a data processing unit of a DC protective device, wherein the data processing unit comprises a DC data processing unit and an AC data processing unit; 2) setting an analog AC rectifying module in the data processing unit, obtaining analog rectifying electric quantity by an AC electric quantity through the analog AC rectifying module, andjudging whether the DC system goes wrong or not by mutually verifying the analog rectifying electric quantity and a DC electric quantity acquired in the DC protective device; and 3) when the analog rectifying electric quantity and the acquired DC electric quantity both change, judging that the DC system goes wrong by combing specific criteria at the same time, and giving a trip instruction. The method can solve the problem of incapacity of quickly and accurately judging whether the DC system goes wrong or not due to small DC sampling value.