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This study examined the impact of four variables—end-hooked steel fiber (HSF), polypropylene fiber (PPF), fly ash (FA), and silica fume (SF)—on the mechanical properties of high-strength concrete. The experimental design was established through orthogonal analysis, supplemented by one-way tests. Subsequently, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction micro-tests were conducted to explore the correlation between mechanical properties and microstructural characteristics, elemental compositions, and hydration products. The findings indicated that polar analysis determined the significance of the four factors in influencing compressive strength, flexural strength, and splitting tensile strength in the following order: HSF > FA > SF > PPF; HSF > PPF > SF > FA; and HSF > PPF > FA > SF. The one-way test analysis indicated that the ideal dosages of 0.36%, 5%, and 7.5% for HSF, FA, and SF led to increases in compressive strength of 30.26%, 4.17%, and 18.19%, respectively. Additionally, the optimal dosage of 0.15% for PPF resulted in a 12.79% increase in splitting tensile strength. Additionally, microscopic examinations revealed that the optimal mix exhibited a higher content of hydration products, a denser interface transition zone, and a reduction in undesirable pores and cracks.