The shear performance, crack resistance and high temperature rheological properties of basalt fiber reinforced bitumen mastics with different sizes and contents of basalt fiber were investigated. Their microscopic mechanism was analyzed by scanning electron microscope(SEM). The result shows that the basalt fiber greatly influences the ultimate tension of bitumen mastics（around 45 times as great as original pitch at best） and significantly improves the high temperature rheological properties. The PG standard is promoted from PG70 to PG76. A network structure was formed by bitumen at both ends of the fibers which was able to disperse stress and contributed to the stability of bituminous mixture.