Suspended particle size is an important marine optical parameter. In Yellow Sea and Bohai Sea, suspended particle size plays an important role in marine biogeochemical processes and ocean color remote sensing, since a large quantity of sediments dominate water composition in this study area. Using 47 in situ samples collected in May and November 2014, based on Geostationary Ocean Color Imager (GOCI) band, a novel inversion model is developed to estimate the median diameter (D50) of suspended particle sizes, by means of remote sensing reflectance (Rrs). The obtained results indicate that a power model by Rrs(555 nm) performs best, coefficient of determination R2 is 0.72, mean absolute percentage error SMAPE is 6.35%. As for model validation, the root mean square error (SRMSE) by using the independent dataset shows a value of about 0.17, and the relative errors ranged from -5% to 5%. The robustness of the developed models is investigated by introducing 5% random error into original data, and the corresponding results show that SMAPE is below 2%, and SRMSE is less than 0.002. Additionally, the model is successfully applied to derive distribution map of D50 from GOCI data (Jun, 2013), and the results show that the diameters of suspended particles increas from near-shore region to off-shore waters.