In view of the problems of large weight and poor economy of ballast blocks in the sand-wave imitating soft mattress used in Jingjiang waterway regulation project，this paper develops a new type of ballast block on the basis of the ordinary ballast block.To analyze and compare hydrodynamic characteristics of the two kinds of ballast blocks，this paper uses a three-dimensional precise numerical simulation method to analyze the hydrodynamic characteristics of the two kinds of ballast blocks from three aspects of mainstream direction velocity，shear velocity，and turbulent kinetic energy，respectively.The paper concludes that the new ballast block still presents better hydrodynamic characteristics while saving 19.8% of concrete consumption.The research results can provide support for the ballast block design of the soft mattress.