High-strength concrete incorporating macro-fiber combines high compressive strength of the matrix, strain-hardening, and multiple crack characteristics. Also, calcite sediment remediation bacterial techniques can enhance the mechanical properties, reduce concrete deterioration, and prevent corrosion of steel reinforcement in both the short-term and long-term. In this paper, The Bacillus subtilis bacteria at an optimum dosage of 105 cells/ml of mixing water was incorporated into M60 and M80 concrete strengthened with 0.5% macro synthetic-fiber content. The performance of 32 simply supported reinforced concrete beams with rectangular-section were evaluated numerically using ANSYS. In this study, the properties of matrix components are considered for different geometric sizes as slender and short beams with different longitudinal reinforcement ratios. The results showed that the bacterial participation in fibrous concrete beams had more significant enhancement in the initial cracking load, ultimate load, moment capacity ratio, ductility ratio, and flexural toughness compared to associated conventional concrete.