Based on the observation of webbulb, drybulb, blackglobe temperatures, and the simultaneous air temperature, wind speed and relative humidity records of the adjacent AWS of Guangzhou in September 2009 to March 2010, study is carried out of the features of Wet Bulb Globe Temperature (WBGT) index of Guangzhou and two kinds of forecasting equations-a daytime and nighttime forecasting method and an hourly forecasting method. Then the forecasting errors of the two kinds of methods together with the initial equation imported from Hongkong Observatory are analyzed, and results show that, the initial Hongkong equation has the biggest error, and the hourly forecasting method constructed based on the hourly fitting has the least error; The three methods all have less errors in nighttime than in daytime, and errors of both daytime and nighttime forecasting method and hourly forecasting method are less than 1℃. Compared with the daytime and nighttime forecasting method, the hourly forecasting method has the similar errors in nighttime and much less errors in daytime. Therefore, based on these, the hourly forecasting method is applied in the meteorological service of the equestrianism of Guangzhou 2010 Asian Games. In the end, the forecasting error of WBGT equation is discussed based on the forecast error of temperature and relative humidity.