In　order　to　study　the　performance　of　a　biomass-fed　gasifier,　a　gasification　model　was　established　based　on　chemical　equilibrium.　In　this　model,　sewage　sludge　with　different　water　content　was　used　as　feedstock.　Air　was　introduced　into　the　gasifier　as　a　gasifying　agent.　The　objectives　of　the　model　were　(a)　calculating　the　equilibrium　temperatures　in　the　gasifier;　(b)　calculating　syngas　compositions　and　heating　values　at　corresponding　equilibrium　temperatures;　(c)　finding　out　the　effect　of　moisture　content　in　the　sludge　and　equivalence　ratio　on　the　gasification　process;　and　(d)　using　a　mixed　feed-stock　instead　of　single　feedstock　to　improve　syngas　yield.　The　model　was　built　in　MATLAB　and　Cantera.　Elements　balance,　chemical　equilibrium,　and　enthalpy　balance　were　used　in　the　model.　For　1　kg　sludge,　the　moisture　contents　of　sludge　range　from　0.1　to　0.8,　and　the　equivalence　ratios　range　from　0.5　to　4.　The　results　show　that　(a)　when　moisture　content　=　0.1,　ER　=　2.47,　the　CO　yield　reaches　maximum　value　of　17.548　mol/(kg　sludge);　(b)　when　moisture　content　=　0.1,　ER　=　2.83,　the　H2　yield　reaches　maximum　value　of　20.756　mol/(kg　sludge).　Gasification　performance　can　be　improved　by　mixing　sludge　with　lignite.　For　1　kg　mixture,　the　results　show　that　(a)　the　maximum　yield　of　CO　increases　from　3.04　to　12.3　mol/(kg　mixture)　with　the　increase　of　lignite　content　from　10%　to　40%;　(b)　the　maximum　yield　of　H2　increases　from　13.75　to　21.88　mol/(kg　mixture)　with　the　increase　of　lignite　content　from　10%　to　40%.　©　2021　Desalination　Publications.　All　rights　reserved.