The choice of power supply radius for transformer substations is a complicated problem. A fuzzy geometric programming model of power supply radius under the fuzzy environment, including problems of soft constraints and fuzzy functions with fuzzy coefficients, is built in order to determine the best choice with less investment and lower energy loss. From the model built in this paper more information can be collected and more satisfactory results can be obtained compared with other static and dynamic optimum mathematical models such as controlling models and classical geometric programming ones.