The author analyzed the working characteristics of special turbine for cooling tower basing on the difference between the special turbine and the conventional hydraulic turbine. This paper points out that the special turbine works in a pressure water system and has typical ultra-low specific speed characteristic. These characteristics determine the type and parameters selection of the special turbine. Based on the theory the author has designed some special turbines in many projects in China. The practical operation shows that the turbines have high energy conversion efficiency and are steady in operation, with fairly good matching of the fans.