The invention discloses a feedback circuit for a switching power source. The feedback circuit comprises a first feedback branch (100), a second feedback branch (200), a third feedback branch (300), aPID adjustment circuit (07), and an isolation circuit (08); the feedback circuit for the switching power source of the invention has the advantages of simplicity, low cost, and the like, can adjust avoltage piecewise according to the different applications of output; MCU programming is not required, and therefore, the complexity of the system can be reduced, and the stability of the system can beimproved. The feedback circuit for the switching power source is of great practical significance in some special applications.