The downwelling diffuse attenuation coefficient (K_d) plays a critical role in underwater light field. It determines the euphotic depth, and affects the distribution characteristics of phytoplankton and primary productivity. Based on in situ data collected from 4 cruise surveys in Lake Taihu during 2008-2013, both the variations and driving factors of K_d were analyzed, and an algorithm to estimate downwelling diffuse attenuation coefficient at 490 nm for a variety of satellites' data was developed and validated. The results show that:(1) suspended particular inorganic matter is the decisive factor of K_d in Lake Taihu;(2) the algorithm of red-green band ratio is the most suitable for estimating K_d(490) in Lake Taihu (N=72, R²=0.72, RMSE=0.89 m^-1, MAPE=21.58%);(3) with the simulated remote sensing reflectance of the main sensor bands such as MODIS/EOS, OLCI/Sentinel-3, GOCI/COMS and MSI/Sentinel-2, the red-green ratio algorithm to estimate K_d(490) was established for a variety of remote sensing sensors(N=72,R²>0.7,RMSE<0.9 m^-1,MAPE<22.0%), and the validation was good as well(N=37,R²>0.7,RMSE<0.9 m^-1,MAPE<22.0%).