The invention discloses a failure circuit suitable for a nonlinear regulator. According to the failure circuit, a first operational amplifier, first, second and third resistors, and a pair of two-channel analog switches constitute an inverting proportional operational amplifier circuit with two different proportional gain coefficients. A window voltage comparator is used to respond to a non-sensitive region, and the proportional gain coefficient output is selected by the pair of two-channel analog switches according to a response signal. As the proportional gain coefficient is obtained using the operational amplifier and the resistors which are linear elements, the non-sensitive region will be neither instable nor inaccurate. The problem that the existing failure circuit has low precision, poor anti-interference ability and poor response is solved.