Sand is a typical particle structure. The effective stress and corresponding deformation are both determined by the particle characteristics of the medium skeleton, and the changeable condition of the particles will further affect the mechanical response of the earth pressure cell in the test process. To correctly measure the earth pressure value, micromechanical method was applied to analyse the force chain formed by the particles contact under loading unloading condition, and the transferring process, the force strain curve and relationship between the cell mechanical response and the ideal response curve were analyzed in detail, which verified the above mechanical response model based on Particle Flow Code (PFC) method. According to the structural characteristics of the sand and above numerical model, the loading condition, porosity, friction coefficient between the particles and stiffness of the earth pressure cell affecting mechanical response of the earth pressure cell were deeply investigated, the numerical results indicated that there were obvious hysteresis and strain irreversibility for the response curve, and the measured value was sensitive to the above factors. Therefore, research on the force chain structure and corresponding evolution law brings forward a scientific base and new research means for understanding its micromechanical characteristics, and different factors influencing the earth pressure cell are also important for cell calibration and practical monitoring to get more correct earth pressure value.