Industries often employ heterogeneous computer aided tools (CAD/CAE/CAM) to carry out complex product designs and simulations resulting in a need for data sharing, data exchange, and computational activities. Nowadays the concept of "Design for Sustainability (DfS)" heightens this challenge, as most DfS approaches especially the Life Cycle Assessment (LCA) involve large amounts of data collection, sharing and computation tasks throughout the product life cycle. ISO 10303, also known as STEP (STandard for the Exchange of Product model data), has evolved for several decades and provides a set of standards for industrial automation systems and integration. In this paper, we propose a STEP-based collaborative framework to integrate heterogeneous CAD tools, LCA tools and other necessary computational tools to support cooperative product design for sustainability. The geometric information from CAD tools and the material/process information from material/process databases are formally represented in suitable STEP application protocols (APs). An agent is implemented to parse the geometric and non-geometric information encoded in STEP data format, and compose them into a complete product tree represented with a NIST CPM (Core Product Model) based information model. The information in the product tree is then evaluated by a LCA tool to obtain environmental impact score. The feasibility and benefits of the proposed methodology have been illustrated with a typical stapler product.