An insulation detection method, which is based on an insulation resistance detection circuit comprising a battery pack, a switch unit and a load; wherein a terminal of the load connects a positive electrode and a negative electrode of the battery pack respectively through the switch unit; the battery pack and the load being respectively connected on different sides of the switch unit; the circuit further comprises a controller, a first sampling point and a second sampling point; wherein the first sampling point is a connection point between the positive electrode of the battery pack and the switch unit, the second sampling point is a connection point between the switch unit and the negative electrode of the battery pack, and the controller respectively connecting the first sampling point and the second sampling point; the method comprising: calculating, when the switch unit is open, a first equivalent resistance (Rp) and a second equivalent resistance (Rn); wherein the first equivalent resistance (Rp) is an equivalent resistance of the positive electrode of the battery pack relative to a reference potential terminal (Vr), and the second equivalent resistance (Rn) is an equivalent resistance of the negative electrode of the battery pack relative to the reference potential terminal (Vr); taking the less one of the first equivalent resistance (Rp) and the second equivalent resistance (Rn) as a first insulation resistance; wherein the first insulation resistance is an insulation resistance of a high voltage circuit on a side where the battery pack locates relative to the reference potential terminal (Vr); closing the switch unit when the first insulation resistance is normal, and calculating a second insulation resistance according to the first equivalent resistance (Rp), the second equivalent resistance (Rn), a voltage of the first sampling point and a voltage of the second sampling point when the switch unit is closed; wherein the second insulation resistance is an insulation resistance of a high voltage circuit on a side where the load locates relative to the reference potential terminal (Vr); determining an insulation state of the high voltage circuit on the side where the load locates according to the second insulation resistance. calculating, when the switch unit is open, a first equivalent resistance (Rp) and a second equivalent resistance (Rn); wherein the first equivalent resistance (Rp) is an equivalent resistance of the positive electrode of the battery pack relative to a reference potential terminal (Vr), and the second equivalent resistance (Rn) is an equivalent resistance of the negative electrode of the battery pack relative to the reference potential terminal (Vr); taking the less one of the first equivalent resistance (Rp) and the second equivalent resistance (Rn) as a first insulation resistance; wherein the first insulation resistance is an insulation resistance of a high voltage circuit on a side where the battery pack locates relative to the reference potential terminal (Vr); closing the switch unit when the first insulation resistance is normal, and calculating a second insulation resistance according to the first equivalent resistance (Rp), the second equivalent resistance (Rn), a voltage of the first sampling point and a voltage of the second sampling point when the switch unit is closed; wherein the second insulation resistance is an insulation resistance of a high voltage circuit on a side where the load locates relative to the reference potential terminal (Vr); determining an insulation state of the high voltage circuit on the side where the load locates according to the second insulation resistance.