Abstract: In order to describe the micromechanical behavior between particles of three-dimensional particle system, using ceramic pellets as the object of study, the three-dimensional particle system in-situ loading experiments was conducted by micro-CT to obtain two-dimensional image sequences of particles with a downward pressure displacement interval of 0.2 mm. The digital volume image of the particle system is obtained by three-dimensional reconstruction, and the pore network model of three-dimensional particles is constructed to calculate the inter-particle contact information under different loading states. Based on the quantitative statistics of the contact information, a characterization method to measure contact force by the particle contact area is proposed, the change law of mechanical properties of the particle system is analyzed from the new perspective of contact area, vertical angle, vertical force, coordination number, etc. The intrinsic connection between inter-particle mechanical behavior and evolution of force chain in three-dimensional particle system is described. The information of strong contact particles was extracted and the change of particle position coordinates was compared. The results show that: during the loading process, the number of contacts shows a decreasing trend, the strong contact accounts for 1/3 of the total number of contacts, and the average contact area is basically unchanged. The number of vertical angles \theta < 45^o and \theta > 45^o in the particle system is maintained at 2:3. The vertical force is the result of the joint action of contact force and vertical angle, its value is more significantly influenced by the vertical angle. The average coordination number showed an overall decreasing trend, the number of particles with coordination number of 3, 4 and 5 accounted for about 70%. In addition, the contact positions of particles and indenter influences change of the strong contact particle coordinates, the region near new contact points is often accompanied by renewal of contact behavior.