In order to reveal the influence of steel fiber type on the bonding performance of ultra-high performance concrete (UHPC) matrix, 10 groups of double fibers pull-out tests were carried out with different straight circular fiber diameters (0.2 mm and 0.3 mm) and mixing amounts of silica fume as variables. The results show that with the increase in the mixing amount of silica fume, the pull-out load, pull-out work, and bond strength of the straight circular fiber with a diameter of 0.3 mm follow a trend of first increasing and then decreasing. When the mixing amount of silica fume is 20%, the utilization rate of steel fiber reaches its peak of 43%. A further analysis was made on the effect of the mixing amount of silica fume on straight circular fibers with a diameter of 0.2 mm, and it is found that the variation of evaluation parameters (such as pull-out load, pull-out work, and bond strength) is completely opposite to that of 0.3 mm fibers. Although the load-slip curves of the two kinds of steel fibers show some similarity in trend, the curves of the straight circular fibers with a diameter of 0.3 mm are relatively full, and there are many peaks and troughs. To sum up, both the steel fiber diameter and the mixing amount of silica fume largely influence the bonding performance of UHPC. This finding not only deepens the study of the internal mechanism of UHPC composites but also provides valuable reference for further optimizing the overall performance of UHPC and exploring its wider applications.