Abstract: Numerical simulations of wood chips combustion process and emission were performed in order to predict the process of combustion and emission under different conditions using Navier-stokes equations, species transport equations, energy conservation equation, RNG k-εturbulent closure and the joint PDF equations, as well as Lagrangian-Eulerian two-way coupling and discrete transfer radiation model for discrete phase particles. The numerical simulation of the composition of CO, CO2 and O2 , velocity and temperature field can provide the basis to improve the efficiency of gasification and combustion of wood chips, and the efficiency of co-firing of municipal solid waste and wood chips. When the primary air is only supplied, the temperature at the exit of secondary combustion chamber is higher and the CO concentration in exhaust gas is higher, too. However, the rate of burnout is improved evidently with staged air-supply and smaller excess air coefficient.