Life Cycle Assessment(LCA) is known as a method investigating the potential effects of products or any processes on the environments. LCA is composed of goal & scope definition, inventory analysis, impact assessment and interpretation. The evaluation stages for the LCA are raw material collection, manufacturing products, transport, usage and recycle or disposal. In this study a LCA methodology is proposed based on the concepts that materials and energy used are converted into various types of wastes and that the wastes generated affect the environment. The wastes released are classified into gaseous, liquid and solid types. The environmental burden factor for each chemical compound in the wastes is introduced to assess the effect of hazardous waste on the environment during the LCA procedure. Results show that the proposed evaluation method of environmental impact in LCA provides the quantified criteria for the improvement of products and processes. A case study is presented to address the advantage of the proposed LCA method.