Abstract: Based on the particle flow theory，the model of backfill sample was created by PFC software and the numerical simulation experiment of uniaxial compression was carried out.The control variable method was used to conduct the sensitivity analysis of several mesoscopic parameters，such as parallel bond strength，particle stiffness ratio，grain composition，friction coefficient，etc.to find out the influences of mesoscopic parameters on macroscopic properties.The results show that:Parallel bond strength mainly influences the strength of the backfill，less effect on the elastic modulus；The increase of particle stiffness ratio may increase the effect of rigid contact of particles and reduce the role of parallel bond，which is mainly shown as tension failure；The friction coefficient mainly affects the strength of the backfill.The larger friction coefficient may induce the stronger bite force between particles and heavier residual strength of sample after the destruction；Parallel bond strength has the largest influence on the strength of the backfill.The results have a great guiding significance in matching the compressive strength，elastic modulus and other macro parameters to micromechanics parameters of the backfill，which can lay the foundation for the debugging and modeling of the mesoscopic parameters.

Key words: Backfill, Particle flow, Mesoscopic parameters, Sensibility, PFC