The invention discloses a no-voltage delayer of an undervoltage coil of a circuit breaker. The no-voltage delayer comprises a transformer T, a charging circuit and a time delay circuit. The charging circuit and the time delay circuit are connected with the transformer T. The charging circuit comprises a relay J, a capacitor C1, a capacitor C2, a resistor R2 and a rectifier bridge D1. The time delay circuit comprises a capacitor C3, a resistor R1, a resistor R3, a switch K1, a switch K2, a rectifier bridge D2 and a triode S. The rectifier bridge D1 of the charging circuit is connected to a secondary winding of the transformer T. The switch K1 of the time delay circuit is connected to the secondary winding of the transformer T. In this way, the no-voltage delayer of the undervoltage coil of the circuit breaker is installed on the circuit breaker, so that the original circuit breaker achieves the undervoltage delay function, installation is extremely easy and convenient, and reliability is better.