As the concept of sustainable development has gained popularity, green building decoration design has gradually become the focus of the construction industry. However, this field still faces problems such as cost constraints and inconsistent performance of materials and equipment. This paper aims to explore how to use computer simulation technology to solve the above problems. First, computer simulation technology is used to simulate and analyze the building’s energy consumption, lighting, ventilation, etc. during the design phase, and the design is optimized to reduce material use and energy consumption, thereby reducing costs. Second, simulation technology is used to predict and verify the performance of materials and equipment, and cost-effective materials and technologies are selected to ensure the building’s energy efficiency and environmental performance. BIM technology is used as the core tool, combined with Autodesk Revit, IES VE software and Rhino/Grasshopper to carry out energy consumption simulation, sunlight analysis, natural ventilation simulation and parametric design. The results show that computer simulation technology is superior to traditional methods in terms of initial investment, operating costs, maintenance costs, energy savings and expected benefits. In terms of material performance matching using computer simulation technology, the matching of tensile strength can reach 95.4%, and the maximum fresh air volume in the ventilation effect can reach 318 m3/h. Computer simulation technology has significant economic and environmental benefits in green building decoration design, and provides important practical significance and theoretical value for the global implementation and development of green buildings.