This paper analyzes temporal and spatial process, and problems based on data between 1986 and 2010. Conclusions are as follows. Power supply of Guangdong relied more on distant outer-province power grids over time, not inner-province ones, close ones or independent power plants. This accelerating enlargement of power supply range could well satisfy its increasing power consumption. However, power production of western provinces couldnt simultaneously meet their own increasing demand and demand by Guangdong. Furthermore, total power transmission and electricity tariff were fixed by long-term framework agreements signed among governments, in which the transmission amount was too much while the tariff was too low, forcing the western provinces limiting their domestic demand without proper compensation. So the current enlarging trend of power supply range of Guangdong is unsustainable and its necessary to introduce power market mechanism through adjusting short-term total power transmission and power tariff according to the market situation.