Non-isothermal thermogravimetry method was used in the paper to investigate the gasification properties of four biomass chars. The chemical composition and microstructures of biomass chars were analyzed by chemical analysis, scanning electron microscope (SEM) and BET method. The results show that the initial gasification temperature (T-0.1) and total gasification temperature (T-0.9) of peanut shell char (PS-char), corncob char (CC-char) and bamboo char (BB-char) are close, and rice shell char (RS-char) has relatively higher T-0.1 and T-0.9. Gasification reactivity of biomass char is in the order of BB-char > CC-char > PS-char > RS-char. It has been confirmed by chemical analysis and microscopic structure analysis that there is a good correlation between the biomass char gasification reactivity and the alkali index; that is, the greater the alkali catalytic index, the higher the catalytic effect. The random pore model (RPM), volume model (VM) and unreacted shrinking core model (URCM) were used to fit the experimental data. The results show that the experimental data agree better with the RPM than with other two models. The apparent activation energies of non-isothermal gasification of PS-char, CC-char, BB-char and RS-char calculated by RPM are 238.6 kJ/mol, 302.7 kJ/mol, 284.9 kJ/mol and 242.2 kJ/mol. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.