Abstract: The corresponding relationship between the macroscopic and mesoscopic parameters is investigated through theoretical analysis and numerical simulation method. Based on the results of a large number of three-dimensional particle flow code numerical tests, the method for determining the mesoscopic parameters which match the porosity, internal friction angle and compression modulus of sand is successfully proposed, and the theoretical formulae between mesoscopic and macroscopic parameters are also given. A three-dimensional particle flow analysis model for pile foundation is established according to the proposed mesoscopic parameters. The load-settlement characteristics and soil displacement field around piles are simulated. The simulated results have a good consistency with the laboratory model tests, and the reliability of the proposed method for macroscopic and mesoscopic parameters is validated. The reasearch results provide a strong foundation for the further study on mesoscopic working properties of pile-soil-cap.