The chromophoric dissolved organic matter (CDOM) in the water is an important source of organic nutrients such as nitrogen and phosphorus in the lake ecosystem. It is a challenge to use the satellite data to inverse the CDOM concentration in inland water. Based on the in situ observations in Lake Dianchi (September 2009 and April 2017) and Lake Taihu (July 2016), and experiments in the laboratory and on the basis of analyzing the inherent optical properties of water bodies, this paper introduces a machine learning algorithm, the random forest inversion model of CDOM concentration in inland lake water, was established based on Sentinel-3A OLCI sensor. The inversion accuracy of the random forest model and other commonly used model such as band ratio model, the first order differential model, the semi-analysis model and the BP neural network model are evaluated by using an independent verification data set. The results show that the mean square error of the random forest model is 0.14 m^-1, with a mean relative error 21%. Compared with the BP neural network model with relatively good inversion effect, the root mean square error is reduced by 50% and the mean relative error is reduced by 38%. The accuracy of inversion has been significantly improved. According to the characteristic parameters of the random forest algorithm, the influence of the respective variables is provided, it is found that the contribution rate of B11 (709 nm) and B6 (560 nm) is the largest, which is the sensitive band of CDOM. Finally, the random forest model was applied to the Sentinel-3A OLCI image in Lake Dianchi on April 12, 2017 and Lake Taihu on May 18, 2017, the distribution of CDOM concentration in the two lakes were obtained. The distribution of CDOM concentration in Lake Dianchi show that the northeast and the southwest region is higher than that in the central and western region. Meanwhile, the CDOM concentration in estuarine is higher than that in the lake water, which indicates that the input of runoff brings a lot of CDOM to Lake Dianchi. The distribution of CDOM concentration in Lake Taihu show a trend that higher in the west region while lower in the middle and east region. The western part of Lake Taihu and the Meiliang Bay in the northern part are greatly affected by the rivers inflow, resulted in a high CDOM concentration, although such influence is gradually reduced for the open area far from the estuary. The CDOM concentration in the eastern Lake Taihu is low due to the abundant aquatic plants and clear water.