Abstract: The possible negative impact on environment caused by microelements from coal bottom ash is one of the key concerns on bottom ash disposal and its reutilization. The release regulation of microelements from bottom ash under rainfall condition was studied in laboratory. Experimental treatments were bottom ash, bottom ash+lime, bottom ash+lime+cow manure, as well as the incubation of bottom ash+lime+cow manure mixture, respectively. The experimental data indicated the maximum concentrations of B, Sr, Ba and Li in leachate were higher than 1 mg/L, and the concentrations of other microelements were lower than this value. The application of lime increased concentrations of B and Ba but decreased those of Li, Mo and Cr in leachate. The application of cow manure and the incubation of bottom ash and cow manure mixture increased concentrations of B, Mo, Zn, V, Cu, Ni, Cd, As, Mn, Ti, Co, Sn, and Se, but decreased those of Sr, Ba, Li, and Cr. Except V, the concentrations of all microelements in leachate decreased with the increase of leachate volume. Chromium, Zn, Cd, Cu and As possibly are the main microelements from bottom ash that may impose potential adverse impact on environment.