The invention discloses a transformer remanence detection and demagnetization method which comprises the following steps: collecting residual flux content of a test transformer, and inputting the residual flux content into an intelligent analysis system; reading the residual flux content of the test transformer through a human-computer interaction interface, and inputting corresponding control instructions; controlling the output of a frequency conversion voltage-regulating unit through the control instructions; and outputting by the frequency conversion voltage-regulating unit a low-frequency AC voltage required for demagnetization, and carrying out demagnetization on the test transformer. The invention also discloses a transformer remanence detection and demagnetization device which comprises an AC power supply module, a power supply conversion module, a DC power supply module, a control acquisition module, the frequency conversion voltage-regulating unit, a man-machine interaction unit, a data acquisition module, the intelligent analysis system and the test transformer. The low-frequency AC voltage is utilized for demagnetization, thereby reducing power capacity and size of the demagnetization device; and through the man-machine interaction unit, operation personnel can obtain the demagnetization processing progress accurately and visually, and input the corresponding control instructions, thereby realizing thorough demagnetization of the test transformer.