The invention discloses an Alternating Current (AC) dimming and emergency power supply method. When there is commercial power, a Pulse Width Modulation (PWM) pulse module controls a relay to switch off dimming AC output by a dual-operational amplification module and an AC signal sent by a central processor module, and at this moment, AC of the commercial power supplies power to a Light-Emitting Diode (LED) illumination module through an LED driving module and simultaneously charges a storage battery through a voltage stabilization charging module; and when there is no commercial power input, the central processor module outputs and transmits a positive power signal to the relay through the dual-operational amplification module, and the relay connects the dimming AC output by the dual-operational amplification module with the AC signal sent by the central processor module, and transmits the positive power signal to the AC.