Biomass is a kind of carbon neutral renewable energy source and considered as a potential alternative to fossil fuels. Thermochemical conversion technologies, including direct combustion, fast pyrolysis, gasification, liquefaction, and carbonization, are suitable for large-scaled utilization of biomass. However, there are still many challenges for commercial utilization. With the rapid development of computing technology, the theoretical simulation method is gradually becoming an important tool for mechanism investigation and guiding technology development. In this work, the main challenges for utilization of biomass via thermochemical conversion are summarized generally. Based on these challenges, the modeling methods and applications at different scales from basic molecular modeling to CFD modeling, as well as some other modeling methods, such as life cycle assessment and artificial neural network modeling are reviewed. The applicability and advantages or disadvantages of different model studies are compared and analyzed in depth. In the end, the challenges and prospect of the modeling method for biomass thermochemical conversion are assessed.