The invention relates to a passive zero-flux sampling device for a CVT leaked current, and the device comprises a primary winding and a secondary winding. The number of turns of the primary winding is greater than two, where each turn is provided with a tap. The device also comprises a jack terminal (1), a first connector (L1), and a second connector (L2). One end of the first connector (L1) is connected to the jack terminal (1), and the other end of the first connector (L1) is connected to a tap of a first turn of the primary winding. One end of the second connector (L2) is connected to the jack terminal (1), and the other end of the second connector (L2) is connected to the taps of other turns of the primary winding. When the second connector (L2) is connected to the jack terminal (1), the first connector (L1) is disconnected. The device employs the adjustable primary winding and a high-precision zero-flux mutual inductor, and achieves the high-precision sampling of a leaked current through converting a primary current with big changes into a secondary current signal with small changes.