In this study, the removal of unburned carbon (UC) from the coal bottom ash (CBA) by flotation was studied by explaining the relationship between adsorption characteristic with different solution pH and content of UC for increasing removal efficiency. Therefore some CBA samples were chosen for test and those samples contained 2.73%(sample A), 7.01%(sample B) and 10.49%(sample C) of UC respectively. The column flotation was carried out at the condition of 10 L/min flow rate with the reagents of 500g/ton kerosene and 80g/ton MIBC. The flotation method was employed using each samples ranged from 6.5 to 52g/L. From the adsorption kinetic curves, the rate of UC adsorption increased rapidly as the reaction approached to equilibrium. The isotherm characteristics on the UC adsorption of CBA were S.type, and these curves were fitted to the BET adsorption isotherm. Content of UC and pH influenced the adsorption; adsorption efficiency was high with increasing content of UC and decreased when pH sifted to acid or alkaline conditions.