Based on the thermogravimetric analysis, co-pyrolysis of expandable polystyrene foam plastics (EPS) and three kinds of biomass (bagasse, peanut shell, corncob) were investigated. The result shows that synergistic effects of the co-pyrolysis of EPS/bagasse and EPS/corncob are obvious, but there is no remarkable synergistic effect for the EPS and peanut shell blends. The kinetic analysis indicates that the pyrolysis processes can be described as first order reactions model, a pretty good fitting of experimental data was obtained for all samples. In the EPS and the biomass pyrolysis, respectively, the former can be described as the one first-order reaction model, and the latter can be described as the three consecutive models, while the co-pyrolysis of EPS and biomass needs to be described as the four consecutive models.