The invention discloses a direct current superposition method measurement circuit. The direct current superposition method measurement circuit comprises a to-be-measured cable, a direct-current power source, a first inductor, a first capacitor, a first surge protection device, a transformer grounded protection circuit, a second surge protection device, a low pass filter, a band elimination filter, an ampere meter and a relay, wherein the to-be-measured cable, the direct-current power source, the first inductor, the first capacitor, the first surge protection device, the transformer grounded protection circuit, the second surge protection device, the low pass filter, the band elimination filter, the ampere meter and the relay are connected between a load and a bus of a power substation grounded transformer; one end of the direct-current power source, the first inductor, the first capacitor and the other end of the direct-current power source are sequentially connected; one end of the first surge protection device is connected with the connecting end of the first inductor and the first capacitor to be connected into a neutral point of the power substation grounded transformer, and the other end of the first surge protection device is connected with the connecting end of the first capacitor and the direct-current power source. The direct current superposition method measurement circuit is simple in connection and used for insulation on-line monitoring of a 35 kV cable; damage caused by supersaturation of the power substation grounded transformer can be prevented, interference of the contact potential, the leakage current and noise can be effectively reduced, and the diagnosis accuracy can be improved.