In recent years, demand for circulating cooling water soars, because of the expansion of industry and enterprise scale, and the increase of project construction.Based on the circulating cooling water system of heat workshop in Nanjing, this paper analyzes the working principle, requirement of water and design difficulties such as large water consumption, and lots of water equipments with scattered layout; expounds the background of the project, the program design, technologies and facilities which provides reference for related design of circulating cooling water system.