The compactability of soil plays a very important role in water conservancy project. In order to study the correlation between fine-grained soil’s compactability and particle composition , according to eight water conservancy projects since 2017, we collected data of compaction test and grain size test. Most test samples are collected from a range of about 200 km between Yangtze river and Huaihe river in Anhui province. The correlation between maximum dry density, optimum water content of fine-grained soil and sand-silt-clay data was examined by simple linear regression and binary linear regression. A binary linear regression result was obtained by using clay-silt content as independent variable and maximum dry density and optimum water content as dependent variable while excluding the data of clay content larger than 37%. Results suggest that particle composition is the major factor affecting the compactability of fine-grained soil, while water and gas in soil also have some effects on the compactability at the same time. A good correlation was found between maximum dry density and optimum water content and soil composition while fine-grained soil content is in the range from 10% to 37%. This study will help us to understand the compactability of fine-grained soil meanwhile avoid poor accuracy and artificial factor during compaction test and grain size test.