Abstract: In view of the problem that the roof deformation amount of mines with impact hazards is relatively large,and the cement-based materials sprayed on the coal pillars along the goaf are easy to crack,which makes it more difficult to prevent and control coal spontaneous combustion,based on fiber toughening technology,different lengths and different dosages of sisal fibers are added to cement-based spray air leakage blocking materials to study and develop fiber reinforced type spray air leakage blocking materials.Three point bending,uniaxial compressive strength,brazilian tension,and scanning electron microscopy are used to study the flexural strength,compressive strength,tensile strength,and micro morphologies of sisal fibers in cement-based materials of mortar samples mixed with sisal fibers,and the optimal dosage of sisal fibers is determined.The research results show that fibers with a length of 20 mm have a better gain effect on the mechanical performance of cement mortar than fibers with a length of 6 mm.The optimal dosage of sisal fibers in mortar is 1.5 kg/m~3,and the maximum flexural,tensile,and compressive strengths of the mortar samples are 6.21 MPa,4.00 MPa,and 13.81 MPa,respectively;Sisal fiber can effectively prevent the propagation of microcracks in mortar and delay the propagation of microcracks into macroscopic large cracks.