The invention discloses an emergency power supply mains supply high-speed monitoring system which comprises a mains supply rectifier unit for receiving a mains supply voltage signal and rectifying the mains supply voltage signal to obtain a pulsating direct current voltage signal, a mains supply voltage sampling unit for obtaining a sampled pulsating direct current voltage signal through the voltage sampling of a pulsating direct current voltage signal, a synchronous assisted power supply unit for receiving the pulsating direct current voltage signal and obtaining a stable pulsating direct current voltage signal through voltage stabilizing processing, a signal amplifier isolation unit for carrying out power amplification isolation processing on the sampled pulsating direct current voltage signal, obtaining a pulsating direct current voltage signal which is subjected to power amplification isolation, and outputting the pulsating direct current voltage signal which is subjected to the power amplification isolation. According to the emergency power supply mains supply high-speed monitoring system, the design of the synchronous assisted power supply unit is employed, mains supply is directly supplied to the signal amplifier isolation unit via the synchronous assisted power supply unit, the circuit structure is simple, and the connection is simple.