The invention belongs to the photovoltaic inverter technical field and discloses a double-path MPPT (maximum power point tracking)-based photovoltaic inverter insulation resistance to earth detection system and method. According to the system, the collector of a first power switch tube is connected with one end of a first inductor and the positive pole of a first diode; the base of the first power switch tube is connected with a controller processing unit; the emitter of the first power switch tube is connected with the negative pole of a first photovoltaic cell; the other end of the first inductor is connected with the positive pole of the first photovoltaic cell; the collector of a second power switch tube is connected with one end of a second inductor and the positive pole of a second diode; the base of the second power switch tube is connected with the controller processing unit; the emitter of the second power switch tube is connected with the negative pole of a second photovoltaic cell and the emitter of the first power switch tube; the other end of the second inductor is connected with the positive pole of the second photovoltaic cell; and the negative pole of the second diode is connected with the negative pole of the first diode. According to the system, components such as extra switch tubes, relays and diodes are not required, and therefore, the size and cost of the detection system can be effectively decreased.