The application of the fly ash from solid refused fuel (SRF) power plant for CO2 capture by semi-dry carbonation process have researched as an eco-friendly practicable CO2 reduction technique. To study the effects of humidity on the carbonation kinetics of fly ash, the fly ash was exposed to accelerated carbonation conditions at a relative humidity of 25, 50, 75, and 100 %. The CO2 capture performance of fly ash can be affected by the process conditions (humidity, concentration of CO2, and reaction time). Because of short diffusion length of H2CO3 in water, the semi-dry process shows faster and effective carbonation reaction than wet processes. This study can show the possibility of fly ash application with the semi-dry process for CO2 capture.