The purpose of this research is to predict the total market demand of photovoltaic (PV) system of the world. By using the Grey forecasting model, the results were precise and valid. Then, the sensitivity analysis was conducted to select the most appropriate horizontal adjusting factor (HAF) and to determine the growth type of PV industry. The result showed the HAF was 0.4, which indicated the growth speed is in a low speed but very close to normal speed. The average residual error was 10.5% from 1995 to 2007 compared to the actual value in the same period. Then, the forecasted value from 2008 to 2011 showed an increasing shape and would reach 8554.9 MW in 2011. This research found the growth type of PV industry of the world, offering meaningful information for firms to decide the strategy in the future. For government, the result could also help to implement adequate policies to support the development of PV industry in the future.