In the wake of increasing global concern over environmental change and energy consumption, building energy conservation has emerged as a pivotal issue worldwide. The primary energy consumption in buildings stems largely from air conditioning and heating systems. The efficiency of these systems is significantly influenced by the thermal performance of the building's exterior wall insulation layers. In-depth research and optimized design of these insulation layers' thermal performance are thus critical topics in the field of building energy conservation. However, current research methods encounter limitations in addressing these issues, notably neglecting the impact of thermal bridges on the insulation layers' thermal performance and focusing solely on single parameters in insulation optimization design. This study addresses these challenges by conducting a comprehensive analysis and optimization design of the thermal performance of building exterior wall insulation layers. It includes an analysis of heat transfer through thermal bridges and the optimization of insulation parameters, aiming to provide a more holistic and systematic approach to optimizing the thermal performance of building exterior wall insulation layers. Specifically, this study uses thermal simulation software to conduct three-dimensional simulation of thermal bridges, analyzing the temperature distribution and heat flow in the thermal bridge area. According to international or domestic standards, the linear heat transfer coefficient of the thermal bridge is determined through calculation. By using optimization algorithms, the thermal performance parameters of the insulation layer are optimized in design. Through experiments, specific linear heat transfer coefficient and equivalent heat transfer coefficient of thermal bridges are obtained, as well as the extent of the impact of thermal bridges on overall thermal performance. Meanwhile, based on optimization algorithms, a set of materials and structural parameters that enable the building's external wall insulation layer to achieve higher thermal efficiency is obtained. After optimization, a lower heat transfer coefficient of the external wall insulation layer is achieved, improving the insulation performance of the wall. This paper provides a technical method for the analysis of heat transfer in thermal bridges and the optimization of insulation parameters. It helps architects more accurately assess and improve the thermal performance of building exteriors, which is significant for reducing energy loss and lowering operational costs of buildings. The research results can provide scientific basis for the formulation of building energy-saving standards, especially in terms of thermal bridge effects and external wall insulation performance. These standards are crucial in driving the industry towards higher energy-saving goals.