An insulation detection method, which is based on an insulation resistance detection circuit comprising a battery pack (H), a switch unit and a load; wherein a terminal of the load connects a positive electrode and a negative electrode of the battery pack (H) respectively through the switch unit; the battery pack (H) and the load being respectively connected on different sides of the switch unit; the circuit further comprises a controller, a first sampling point (A) and a second sampling point (B); wherein the first sampling point (A) is a connection point between the positive electrode of the battery pack (H) and the switch unit, the second sampling point (B) is a connection point between the switch unit and the negative electrode of the battery pack (H), and the controller respectively connecting the first sampling point (A) and the second sampling point (B); 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 (H) 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 (H) 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 (H) 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 (A) and a voltage of the second sampling point (B) 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 (H) 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 (H) 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 (H) 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 (A) and a voltage of the second sampling point (B) 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. <EOS>