The invention discloses a detecting method and device for the reversing anomaly of a four-way valve. The method comprises the steps as follows: the water inlet temperature and the water outlet temperature of a unit are detected; the high-and-low relation between the water inlet temperature and the water outlet temperature is determined; the change trend of the water outlet temperature is determined; whether the high-and-low relation between the water inlet temperature and the water outlet temperature and the change trend of the water outlet temperature conform to the running state in the current running mode is judged; and when the high-and-low relation between the water inlet temperature and the water outlet temperature and the change trend of the water outlet temperature do not conform to the running state in the current running mode, the reversing anomaly of the four-way valve is determined. By the aid of the detecting method and device, the reversing anomaly of the four-way valve is detected, the anomaly of the four-way valve is warned in advance, and the warning and protecting effects are realized.