Water is critically important to human life. However, the demands for fresh water in many regions are much more than those can load. The concept of water footprint came from virtual water which can help us roughly understand the water consuming of a product manufacturing process and after services. This paper presents a methodology for assessing water footprint of machine tools. Detail assessment steps and calculation process for life cycle of machine tools is described in this paper. The difficulty in inventory process and ata election during water footprint assessment will be presented. A case study is used to explain the capabilities of the proposed methodology.