The utility model provides a double protector for phase-failure and steering which is used for cutting off automatically the power supply when the power supply circuit of a motor generates phase interruption and wrong phase-sequence connection. The utility model is characterized in that the double protector for phase-failure and steering is provided with a novel pass-band control circuit of voltage amplitude of input signal which is composed of a 556 integrated circuit (containing two 555 integrated circuits), when an inverted sequence voltage wave filter and the signal voltage which is rectified and filtered are in the range of the voltage amplitude pass-band, the motor can work normally, or a control circuit is used to make the motor switched off. The circuit of the utility model is integrally loaded into a control box, and an external sensor is not needed.