Nowadays, in concrete technology, the use of fiber in a concrete mixture is growing extensively. The use of fibers improves the properties and performance of concrete in durable parameters such as crack control and resistance parameters such as increasing energy absorption and increasing modulus of rupture. In this research, macro-synthetic fibers were used. Which was manufactured by sirjan Nano yarn Company. Also, concrete beams with dimensions 15 by 15 by 55 cm were made. The purpose of this paper is to investigate the effect of different amounts of high-strength and high-modulus of elasticity macro-synthetic fibers to investigate the behavior fiber reinforced concrete after cracking. For this purpose, concrete beams with fiber dosage of 0.1, 0.3 and 0.5 were constructed. Flexural strength, flexural toughness, and average residual strength were tested and evaluated according to ASTM C1609 and ASTM C1399 standards. The results of this study showed that the increase in the volumetric percent of macro-polymer fibers has a slight effect on compressive strength. But it has a positive effect on flexural strength, flexural toughness, and the average residual strength.