The invention provides a back-to-back testing circuit based on a DC/DC converter. The back-to-back testing circuit comprises DC buses, a power supply module and a DC/DC converter module. The DC buses are used for connecting the power supply module and the DC/DC converter module in series. According to the back-to-back testing circuit, a back-to-back connection manner is utilized on a tested member; Supplying of one end DC voltage to the tested member is required. Furthermore voltage grade can be selected according to a relatively low rated DC voltage of the tested member. More importantly, two converters can feed most absorbed electric energy back to a power grid, and the power supply part of the testing circuit only supplies a relatively low output current, thereby greatly reducing capacity and manufacture difficulty of testing equipment, and greatly reducing testing equipment cost and operation cost in testing.