The utility model discloses a dual-power automatic transfer switch signal detecting circuit comprising a single-chip microcomputer U1, a comparator U2, a resistor R1, a capacitor C1, a transformer T, a rectifier bridge Q, and a triode VT1. The dual-power automatic transfer switch signal detecting circuit individually detects voltage signals and frequency signals by means of the single-chip microcomputer U1, and performs automatic switching only when the two detection determine that switching can be performed so as to be very low in misjudgment rate. The dual-power automatic transfer switch signal detecting circuit is simple in circuit structure, low in cost, very high in stability, and very suitable for popularization.