Abstract: The present disclosure provides a dimming method and a dimmer. In the dimming method, when a mains power state is switched to an emergency state, a dimming ratio K is used to perform dimming control on a load unit; the dimming ratio K is calculated as follows: K=Psource/Pload. The dimmer includes: an emergency power source power acquisition module, configured to acquire an output power Psource of an emergency power source; a load unit power acquisition module, configured to acquire a power Pload of a load unit in a mains power state; and a dimming signal generation module, configured to acquire a dimming ratio according to K=Psource/Pload when the mains power state is switched to an emergency state, generate a dimming signal according to the dimming ratio K, and output the dimming signal to the load unit. The present disclosure also provides a dimming emergency inverter and an emergency lighting system.