A leakage current detection circuit, comprising a first resistor located on a positive direct current bus, a second resistor located on a negative direct current bus, and a detection processing circuit separately connected to the first resistor and the second resistor, wherein the first resistor and the second resistor are located on a trunk circuit in a system comprising the positive direct current bus, the negative direct current bus, and a load connected between said positive and negative direct current buses, or are located on a same branch circuit in the system; and the detection processing circuit is configured to detect a current flowing through the first resistor, detect a current flowing through the second resistor, and determine a difference between the current flowing through the first resistor and the current flowing through the second resistor as a leakage current; wherein the detection processing circuit is further configured to: when the leakage current is not equal to zero, determine that an insulation fault occurs in a circuit comprising the load and located between the first resistor and the second resistor in the system; and when the leakage current is equal to zero, determine that insulation of the system is normal; wherein, the circuit further comprises a third resistor located on the positive direct current bus and a fourth resistor located on the negative direct current bus, wherein the detection processing circuit is separately connected to the third resistor and the fourth resistor; the detection processing circuit is further configured to detect a current flowing through a third resistor, and detect a current flowing through a fourth resistor; and when the first resistor and the second resistor are located on the trunk circuit in the system, and the third resistor and the fourth resistor are located on a same branch circuit in the system, the detection processing circuit is further configured to: when the current flowing through the third resistor is not equal to the current flowing through the fourth resistor, determine that an insulation fault occurs in a circuit that comprises the load and that is located between the third resistor and the fourth resistor, wherein a leakage current is a difference between the current flowing through the third resistor and the current flowing through the fourth resistor; and when the current flowing through the third resistor is equal to the current flowing through the fourth resistor, and the current flowing through the first resistor is not equal to the current flowing through the second resistor, determine that an insulation fault occurs in a positive direct current bus between the first resistor and the third resistor, or an insulation fault occurs in a negative direct current bus between the second resistor and the fourth resistor, or an insulation fault occurs in a circuit, other than the circuit located between the third resistor and the fourth resistor, namely in a circuit comprising the load and located between the first resistor and the second resistor in the system, wherein a leakage current is the difference between the current flowing through the first resistor and the current flowing through the second resistor; or when the first resistor and the second resistor are located on a same branch circuit in the system, and the third resistor and the fourth resistor are located on the trunk circuit in the system, the detection processing circuit is further configured to: when the current flowing through the first resistor is not equal to the current flowing through the second resistor, determine that an insulation fault occurs in a circuit that comprises the load and that is located between the first resistor and the second resistor, wherein a leakage current is the difference between the current flowing through the first resistor and the current flowing through the second resistor; and when the current flowing through the first resistor is equal to the current flowing through the second resistor, and the current flowing through the third resistor is not equal to the current flowing through the fourth resistor, determine that an insulation fault occurs in a positive direct current bus between the first resistor and the third resistor, or an insulation fault occurs in a negative direct current bus between the second resistor and the fourth resistor, or an insulation fault occurs in a circuit, other than the circuit located between the first resistor and the second resistor, namely in a circuit comprising the load and located between the third resistor and the fourth resistor in the system, and a leakage current is a difference between the current flowing through the third resistor and the current flowing through the fourth resistor.