Abstract: By introducing LCA(life cycle assessment) environmental assessment method to arc welding process,it is presented that the involved material quantity of power,resource and waste per unit volume or mass of welding deposited metal(welding product) can be defined as a technical parameter for environmental load assessment of welding process,which provides a new method to quantitatively investigate environmental load of welding.The results from the environmental load assessment of CO₂ gas shielded arc welding indicate that waste is the key factor which should be controlled and improved to affect the product making environment.The assessment model has been proved reasonable from the fact that power factorial item of CO₂ gas shielded arc welding shows good comparability with correlative item of steel-making process in electric oven,which makes it possible to quantitatively assess the whole life cycle of materials.