Coal/biomass combustion is a major source of submicron particulate matter (sub-PM), with mineral substances in the fuels playing a key role in the formation and growth of these particles. In this study, the temporal evolution of sub-PM is predicted by simulating coal/biomass combustion under different temperature, atmosphere, species, particle size and density conditions by using nucleation, condensation, coagulation and deposition sub-models. Compared with experimental data, the results show that the amount of sub-PM generated from pulverized coal combustion increases with higher temperatures and oxygen concentrations, and lignin (LN) produces the highest emission of sub-PM among different biomass types. The peak particle size distribution (PSD) of sub-PM across different experimental conditions is mainly centered around 0.1–0.2 μm. The values of relative error are below 20% and even below 10%, indicating that the model is in good agreement with the experimental data. Subsequently, the effects of pulverized coal size and coal density on the PSD of sub-PM are predictively simulated by the verified model, the findings indicate that both of the peak PSD are among 0.08–0.23 μm, the emission amount of sub-PM negatively relate to coal size and coal density.