• Basalt fibers can improve the low temperature crack resistance of asphalt mixture. • The Weibull distribution can approximately describe the fiber distribution in basalt fiber asphalt mortar. • Better reinforcement can be achieved by well dispersed basalt fibers. • The spatial distribution of fibers truly influence the flexural tensile properties of asphalt mixture. This study aims to reveal the relationship between the uneven distribution characteristics of basalt fibers and the flexural tensile performance of asphalt mixture. Nano Computed Tomography(nano-CT) was used to explore the realistic distribution features of basalt fibers in asphalt mortar. In addition, the distribution fitting and goodness of fit tests were carried out to find out the distribution form that can well describe the distribution of basalt fibers. The three-dimensional fiber models with different distribution forms were established in finite element software ABAQUS. Then the three-point bending test was simulated to analyze the influence of fiber dispersion and distribution on the flexural tensile properties of the asphalt mixture. Simulation results show that the asphalt mixture beam model shows better tensile resistance when the fibers are better dispersed. Moreover, when more basalt fibers are at the bottom of the middle span, it is more conducive to reducing the peak stress at the bottom of the beam and delaying the cracking of the asphalt mixture.