Most of methodologies, concepts and tools, which integrate Computer Aided Design (CAD) and Life Cycle Assessment (LCA) systems and aim at ecodesigning, are generally oriented to the environmental assessment. The environmental improvement is treated only in a few works; however it is a pivotal phase in the eco-design process. In this paper, we propose a new environmental improvement process based on the remaining Degrees of Freedom (DoFs) for CAD designer on which he can act to eco-design his/her CAD model. The originality in this process is the expression of a CAD model environmental impacts in function of CAD designer DoFs, aiming at help non environment experiment designer to eco-design products in CAD phase. For this, first, we present the concept of DoFs and we use it to identify the CAD designer action zone. Second, we establish the impact matrix of DoFs in each life phase, then; we develop the global impact matrix .The assembly of EIs by linear summation of the matrix columns shows the most impacting ones. Finally, we consider a case study to valid our proposed approach and results are shown in function of DoFs.