According to the traditional view，the semi-deep lake-deep lake area in the lacustrine basin is mainly dominated by relatively homogeneous mudstone shale with high clay and low terrigenous clast，which is a forbidden area for hydrocarbon exploration. But in recent years，the exploration and discovery of shale oil and gas in China and abroad has completely broken through the traditional understanding of the past. In order to research the basic geological characteristics of shale system in fine-grained sedimentary area of the lacustrine basin，based on 635 m cores of Well G108-8，Well GD14 and Well GD12，more than 8 000 analytical laboratory data and matching logging data，the lithologic characteristics，reservoir characteristics，organic geochemical characteristics and their influence on the reservoir stimulation of Kong2 Member in Cangdong Sag，Huanghua Depression were studied. It’s found that the mineral composition of shale system in Kong2 Member is complex and the rock types are diverse. According to the X-ray diffraction（XRD）mineral composition，the shale system can be divided into three categories and seven sub-categories，such as felsic shale，limy dolomite and hybrid shale.Shale system not only has ability to generate oil but also has a certain storage capacity，in which there are many kinds of pores and fractures，such as organic pore，intergranular pore，micro-crack，etc. The shale can be easily stimulated as well.The abundance of organic matter and the maturity of thermal evolution have obvious effects on the porosity development，oil content and carbonate crystallization of shale oil reservoirs. The differences in mineral composition and structure of shale result in differences in petroleum geology among different rocks. Hydrocarbon of short-distance migration should be look for in limy dolomite，while the hydrocarbons of in-situ retention should mainly be look for in felsic shale and hybrid shale. All the three types of shale are beneficial for shale oil storage，but different types of shale should be stimulated by different engineering measures to maximize the exploration and development of shale oil.