The invention discloses a photovoltaic module aging detection method based on power difference transformation. A DC-DC converter is connected onto each photovoltaic battery in parallel, high-level output ends of all the DC-DC converters are connected with the positive pole of a photovoltaic module, low-level output ends of all the DC-DC converters are connected with the negative pole of the photovoltaic module, and whether the photovoltaic batteries age and the aging degree are judged according to the direction and size of input side current of each DC-DC converter. Part of electric energy ofunaged photovoltaic batteries is extracted and injected into the DC-DC converters, and the direction of the input side current of the corresponding DC-DC converters is positive; aged photovoltaic batteries absorb electric energy through the DC-DC converters, and the direction of the input side current of the corresponding DC-DC converters is negative. The method has the advantages of low cost, small size, high accuracy, high detection speed and the like and can be widely applied to the industry field, so that aging of the photovoltaic modules and fault troubleshooting difficulty and costs aresubstantially reduced, and the development of the photovoltaic industry is promoted.