The present disclosure discloses a detection circuit and method. The detection circuit comprises: a controller, a battery pack, a main positive switch module, a main negative switch module and at least one detection loop. The controller collects voltages of a positive electrode and a negative electrode of the battery pack and a voltage between external sides of the main positive switch module and the main negative switch module when turning on the main positive or negative switch module and after turning on any detection loop, and obtains resistance values of insulation resistors of the external sides according to resistance values of insulation resistors of internal sides of the main positive and negative switch module, as well as the voltages of the positive electrode and the negative electrode and the voltage between the external sides of the main positive switch module and the main negative switch module, which are collected twice.