An insulation resistance detection circuit, coupled to a positive end (V+) and a negative end (V-) of a DC power source (Vdc), and configured to detect a positive insulation resistance (Rx) between the positive end (V+) and a ground point (G), and a negative insulation resistance (Ry) between the negative end (V-) and the ground point (G), characterized in that the insulation resistance detection circuit comprising: a first resistance (R1), a second resistance (R2), a third resistance (R3), and a fourth resistance (R4) coupled in series, and a first node (N1) between the second resistance (R2) and the third resistance (R3) coupled to the ground point (G), a switch (SW), comprising a first end and a second end, the first end coupled to a second node (N2) between the first resistance (R1) and the second resistance (R2), and the second end coupled to a third node (N3) between the third resistance (R3) and the fourth resistance (R4), and a detection unit (DET), coupled to any two of the positive end (V+), the negative end (V-), the first node (N1), the second node (N2), and the third node (N3), wherein the detection unit (DET) is configured to set a first estimated resistance of the positive insulation resistance (Rx) and a second estimated resistance of the negative insulation resistance (Ry), and acquire a first voltage (V1) based on turning on the switch (SW) and acquire a second voltage (V2) based on turning off the switch (SW), wherein the detection unit (DET) is configured to calculate a third voltage (V3) and a fourth voltage (V4) according to the first estimated resistance and the second estimated resistance so as to detect the positive insulation resistance (Rx) and the negative insulation resistance (Ry) when the third voltage (V3) is equal to the first voltage (V1) and the fourth voltage (V4) is equal to the second voltage (V2). a first resistance (R1), a second resistance (R2), a third resistance (R3), and a fourth resistance (R4) coupled in series, and a first node (N1) between the second resistance (R2) and the third resistance (R3) coupled to the ground point (G), a switch (SW), comprising a first end and a second end, the first end coupled to a second node (N2) between the first resistance (R1) and the second resistance (R2), and the second end coupled to a third node (N3) between the third resistance (R3) and the fourth resistance (R4), and a detection unit (DET), coupled to any two of the positive end (V+), the negative end (V-), the first node (N1), the second node (N2), and the third node (N3), wherein the detection unit (DET) is configured to set a first estimated resistance of the positive insulation resistance (Rx) and a second estimated resistance of the negative insulation resistance (Ry), and acquire a first voltage (V1) based on turning on the switch (SW) and acquire a second voltage (V2) based on turning off the switch (SW), wherein the detection unit (DET) is configured to calculate a third voltage (V3) and a fourth voltage (V4) according to the first estimated resistance and the second estimated resistance so as to detect the positive insulation resistance (Rx) and the negative insulation resistance (Ry) when the third voltage (V3) is equal to the first voltage (V1) and the fourth voltage (V4) is equal to the second voltage (V2). <EOS>