The bending performance of a concrete beam can be reflected by its macroscopic characteristics of surface crack distribution and evolution during the bending process. The bending behaviors of concrete beams were investigated, and the fractal theory was applied to analyze the development of the surface cracks. Basalt fiber reinforced plastic (BFRP) bars reinforced ultra-high performance concrete with different waste tire steel fiber (WTSF) replacement ratios were used as the concrete matrix. The results show that the distribution of cracks on the surface of concrete beams exhibits fractal characteristics and self-similarity, the fractal dimension is between 0.892 and 1.064. The relationships between the fractal dimension of cracks on the surface of beams and the applied load, WTSF replacement ratio, mid-span deflection and maximum crack width were discussed, and the functional relationships between WTSF replacement ratio and the fractal dimension of the whole beam section and pure bending section under complete failure state were fitted, respectively. It is found that fractal dimension has logarithmic function relationship with applied load, mid-span deflection and maximum crack width. Under the complete failure state, the fractal dimension of cracks on the beam surface increases with the increment of WTSF replacement ratio, but the adverse effect is not obvious on the whole. The results obtained in this study can provide some theoratical basis and practical experiences for the application of ultra-high performance concrete.