Abstract: In order to strengthen the stability of cement paste backfill( CPB),fibers were included into paste filling material( CPFM) to improve its brittleness. The failure behavior of the polypropylene fiber reinforced CPFM was studied by means of macro-meso experimental investigations. At the macro-scale,the influence of polypropylene fiber content on the mechanical properties of CPFM was studied quantitatively by a series of uniaxial compression tests. The influence of fiber on the meso-structure of cement paste backfill specimens was analyzed by the X-ray computed tomography multi-slice scanning technique. The results show that the addition of fibers increases the peak strength of the CPFM slightly at the cement content of 10%. It improved toughness and the strain at peak strength significantly. CT results show that fibers can make cracks finer and more uniform by preventing their expansion and extension,then a larger volume of cracks absorbing more energy exists in specimen before the damage,thus it improves the toughness of CPFM.