Coal bottom ash is used as the catalyst for biomass gasification of palm kernel shell using thermogravimetric analyzer coupled with mass spectrometer at operating temperature ranging from 650 °C to 750 °C. The objective of this study is to evaluate the gas composition of the biomass gasification using coal bottom ash as the catalyst. The produced hydrogen gas content is 36.57 vol at temperature of 700 °C while the gas composition of carbon monoxide, carbon dioxide and methane are 24.73, 1.40 and 37.30 vol respectively. In addition, it is found that the minerals exist in the coal bottom ash help to reduce the formation of carbon dioxide gas while promote the formation of methane in the product gas. Copyright © 2016, AIDIC Servizi S.r.l.