Insulation performance detecting circuit and detecting method

The invention provides an insulation performance detecting circuit and detecting method. The insulation performance detecting circuit comprises a power supply module, a sampling circuit, a matching circuit and a to-be-detected circuit. The sampling circuit, the matching circuit and the to-be-detected circuit are connected in parallel between a positive bus and a negative bus of the power supply module. The output terminals of the sampling circuit, the matching circuit and the to-be-detected circuit are grounded. The sampling circuit is used for collecting a first voltage of the positive bus and a first voltage of the negative bus; the matching circuit is adjusted to collect a second voltage of the positive bus and a second voltage of the negative bus; and the resistance value of a to-be-detected resistor in the to-be-detected circuit is obtained based on the first voltage of the positive bus, the first voltage of the negative bus, the second voltage of the positive bus, and the secondvoltage of the negative b