The low temperature performance of basalt fiber asphalt mortar（BFAM）and mixture was studied by tensile test and bending test, and the correlation of low temperature performance between BFAM and mixture was analyzed. The phase change of BFAM and the microstructure of asphalt mixture were tested and characterized, and the mechanism of improving the low temperature performance of BFAM and mixture by basalt fiber was thoroughly analyzed. The results show that the low temperature performance of BFAM and mixture has a close correlation, and the tensile fracture energy of mortar at -20℃ has the greatest correlation with the bending strain of mixture. Based on the low temperature performance, the optimal content of basalt fiber is recommended to be 04%. The tensile fracture energy of the BFAM with the optimal content of basalt fiber is 46 times that of the ordinary asphalt mortar at -20℃, and the bending strain of mixture is 190% and 250% higher than that of the ordinary asphalt mixture at -10℃ and -20℃. BFAM has good low temperature performance and thermal stability. The glass transition temperature of mortar is 375℃ lower than that of ordinary asphalt mortar, and the heat absorption increases by 01525J/g during the transition from high elastic state to viscous flow state. The internal connection of ordinary asphalt mixture is weak. Basalt fiber enhances the integrity of mixture and restrains the crack propagation, thus improves the crack resistance of asphalt mixture.