In this study, the effects of particle concentration on particle temperature and gasifying agent concentration was analyzed based on the gasification experiments. The gasification processes of different coal chars and petcoke were divided into fast reaction process (gasification of lignite and bituminous char) and slow reaction process (gasification of anthracite char and petcoke). The reactivity index of fast reactions was extremely higher than that of slow reactions. The reaction rate of sparse particle swarms also differed from that of dense particle swarms for the same sample. For fast reactions, the effects of particle concentration on gasification reactivity was limited. It was illustrated that the evident increase of particle temperature and the decrease of gasifying agent played a contrary effect on reactivity for fast-reaction samples. Nevertheless, the slight decrease of particle temperature and evident decrease of gasifying agent concentration led to the decrease of reaction rate with particle concentration for slow-reaction samples.