Steam reforming (SR) and partial oxidation (POx) of nascent volatiles (NV) generated from fast pyrolysis of cedar wood chips in a two-stage reactor were studied numerically. A detailed chemical kinetic model (DCKM) consisting of more than 8000 elementary step-like reactions and more than 500 chemical species was used to simulate pyrolysis at 750°C and reforming of the NV at 900°C in the first and second stages, respectively. The molecular composition of the NV, which is one of the required boundary conditions for computations using the DCKM, was approximated based on analytical pyrolysis experiments. Global reactions accounting for the decomposition of the ill-defined portion of the NV and soot reforming were also tested to improve the model capabilities. The DCKM with the global reaction coupled with a plug-flow reactor model could fairly reproduce the experimentally observed trends for the effects of oxygen and steam partial pressures on the yields of major products such as hydrogen, carbon monoxide, and tar residual rate.