Due to the rising awareness of environmental protection, environmental impact of a product becomes an important design criterion. However, most companies do not have sufficient tools to evaluate the environmental impact of their designs. In this paper, a system to evaluate the carbon emission and cost of product designs is developed to help company determine which design to adopt. For a given design, the assembly structure, assembly sequence, and the supply chain configuration are optimized to minimize the carbon emission. An evolution based genetic algorithm is developed to search the assembly structure and sequence. A dynamic programming based algorithm is developed to optimize the supply chain configuration. To estimate the carbon emission, from cradle to gate life cycle assessment approach is adopted. A real world computer chair examples are used to illustrate the system.