Abstract: Co-gasification of biomass and coal can improve the fluidization of biomass and prohibit the production of tar. This paper applied the Aspen Plus to simulate the co-gasification of biomass and coal in fluidized bed gasifier. To simulate the reality in a fluidized bed gasifier, the gasification reaction kinetics was expressed by FORTRAN subroutine in RCSTRs, and then the RSCTRS in series were used to substitute the Gibbs reactor.The results indicate that the simulating values are well agreed with the experimental data.Through the sensitivity analysis model of Aspen Plus, the effects of steam-to-feed ratio（S/F） on various factors such as gas composition, heating value and gasification efficiency were systematically studied. The simulation results indicate that the increase of S/F value is conductive to improve hydrogen yield.When the S/F value is in range of 0.35~0.45, the high gasification efficiency and heating values could be obtained.