The increase of climate disasters and air pollution has caused an urgent need for the clean and low carbon energy transition. In this background, polygeneration represents an innovative and promising concept. The purpose of this study is to provide a generic modelling and optimization strategy to evaluate the polygeneration systems in urban areas. A biomass polygeneration integrated energy system, providing electricity, heating and cooling as well as chemical product, is proposed and evaluated in this work. The feasibility of biomass polygeneration integrated energy system in different regions is also investigated by case study. A mixed-integer nonlinear programming approach has been formulated in General Algebraic Modeling System to address the following issues: a) selection of technologies, types and numbers of equipment to match the energy demand of end users; b) strategic planning and process designing from both economic and environmental perspectives; c) representation of the relationships and trade-offs between the trigeneration and chemical conversion steps; d) operation strategies for biomass polygeneration integrated energy system with time dependent process and boundary conditions. Moreover, the proposed biomass polygeneration integrated energy system is compared to the conventional natural gas-based combined cooling heating and power system as the reference.