Real time transparency estimation method was studied using AVHRR Channel 1 (Visible band, 0.58 - 0.68 $mu extrm{m}$) digital number (DN) of NOAA Satellite. The relationshop between the measured transparency and the digital number shows following exponential equation in the southeastern Yellow Sea : Tr = 4820 $ imes$ exp (-0.082 $ imes$ DN), 77 $leq$ DN < 105 where Tr is the transparency in meters and DN is the digital number of AVHRR Channel 1. From this equation, real time transparency can be simply estimated using data from the NOAA Ground Station of National Fisheries Research and Development Agency.