The invention provides a secondary circuit insulation detection device. The secondary circuit insulation detection device comprises a housing, a low-frequency signal generator, a terminal, a display,a hand-held mutual inductor and a power supply module; the power supply module is electrically connected with the display and the low-frequency signal generator; the display is electrically connectedwith the hand-held mutual inductor; and the low-frequency signal generator inputs a low-frequency signal into the terminal. According to the invention, power supply to the detection device by the internal power supply module is implemented, and the device does not need to be switched in a direct current system operating in a substation to use a power supply, so as to avoid the wire connection anddisassembling risks and influence of other low-insulativity circuits on detection accuracy.