Today, the use of fibers in concrete is one of the best methods to improve weaknesses such as low tensile strength and brittleness. Polyvinyl alcohol fibers are one of the best fibers to improve the mechanical properties of fiber concrete. These fibers improve the mechanical strength and performance of concrete by the connection between the micro-cracks, which is due to its excellent adhesion, tensile strength and high modulus of elasticity. The main pur-pose of this research is to analyze and evaluate the effect of polyvinyl alcohol fibers with a diameter of 0.014 mm and lengths of 6 and 12 mm in combination in high strength concrete containing microsilica. Accordingly, four mixtures with different amounts of polyvinyl alco-hol fibers (0, 0.15, 0.3 and 0.6% of the total volume of concrete) were evaluated due to their effect on the fresh and hardened properties of high strength concrete. 10% microsilica was used as a substitute for Portland cement in all mixtures. A series of experiments (compressive strength, indirect tensile strength) showed that the low volume of polyvinyl alcohol fibers significantly increases the mechanical properties of concrete. The results of this research show that the use of volume ratio of 0.15% of polyvinyl alcohol fibers increases the compressive strength by 10.29% and tensile strength by 10.43%.