With main functions of pressing, water-filtering, supporting and transporting wet paper sheets, paper-making press felts are important supply material in a paper-making production. Heat setting is one of the most important processes during the felt production. This process has an important effect on the performance and quality of the felts. This paper studies the function and mechanism of the heat setting process. Major parameters of the process, such as heat setting temperature and time in particular, are analyzed and discussed in detail.