The invention relates to the technical field of transformers, in particular to a K-coefficient transformer equivalent load conversion method, which comprises the following steps: Step A: measuring thedirect current resistance RDC of a transformer product winding at normal temperature, and then calculating the direct current resistance loss PDC; Step B: measuring the respective load losses P1 andPx of products under the frequency f1 and the frequency fx, and resolving the winding eddy current loss Pwe1 and the structural component stray loss Pse1; Step C: calculating the total eddy current loss Pwe of the winding according to the K value and the eddy current loss Pwe1; Step D: calculating the multiple IN of the overload current; and Step E: simulating and measuring the equivalent temperature rise of the winding of the product under the corresponding K coefficient harmonic wave. Compared with the UL1561 standard, the method for testing the equivalent load of the K-coefficient transformer is more reasonably defined, and the phenomenon that stray loss Pse in a structural member of the product is mixed into the winding, so that the equivalent loss of the product is high in value and is subjected to transition test is avoided.