Many studies point out that weather conditions involving temperature, wind power, monsoon transform, air pressure, sea condition, tide, ocean current, salinity, eutrophic environment and so on are key factors causing Red Tide. In the red tide high frequency areas of the South China Sea, the eutrophic environment of sea water has already existed, so the key elements such as meteorological and hydrological conditions play an importance role in the occurrence of red tide. The atmospheric circulation maintenance and variation decide whether meteorological phenomena, and hydrological key elements stabilize or change. Moreover, the red tide organisms＇ breeding from the initial stage to the blooming reproduction stage, until reaching the biological density of the red tide, generally takes 4 - 5 days. In the paper, the red tide examples are analyzed in the past 10 years, and the weather circulation situation and hydro-meteorological key elements of it are counted to find the previous circulation mode and bring out important factors inducing the blooming of red tide. The predicted result in 2003 according to this method was satisfactory.
