Abstract: Secchi disk depth is an important optical characteristic of water and a vital index in marine water quality survey. In this paper,we developed and adapted empirical and semi-analytical algorithms to eatimate Secchi disk depth in the Yellow Sea and the East China Sea. The development of the algorithms is based on in situ observations and MODIS remote sensing reflectance data. The three-band model was most suitable for monitoring Secchi depths in this region, with a determination coefficient (R²) of 0.719, relative mean square error (RMSE) of 1.47 m and a mean relative error (MRE) of 19%. Empirical algorithms proves to be more robust than semi-analytical in this study. Using satellite imagery and the proposed model, one can derive maps of water clarity in the study area.