Aspen Plus software combined with Fortran programming was employed to study gasification of biomass via air based on a fixed bed reactor, and pine, corn stalks, sawdust were selected as gasification feedstock. The effects of equivalent ratio (ER) and biomass moisture content on dry gas lower heating value, gasification temperature, dry gas composition and exergy efficiency were examined. The results showed that when biomass moisture content was at a certain value, along with the increase of ER, CO content rose up first and then decreased, H2 content decreased, dry gas lower heating value declined and gasification temperature increased while exergy efficiency rose up first and then decreased, when ER was constant, along with biomass moisture increased, CO content decreased, H2 content rose up first and then decreased, dry gas lower heating value declined while gasification temperature decreased first and then increased. Under the biomass moisture of 20%, the maximum exergy efficiency for gasification process of pine, corn stalks and sawdust was 61.67%, 60.23% and 54.98%, respectively, and the corresponding ER 0.25, 0.2 and 0.15, respectively.