Abstract: In this study, the theoretical method of measuring the bending strength of the composite material consisting of epoxy and phenol formaldehyde resins with aluminum oxide nano-particles was used with different weight ratios (10, 30, 50%) of woven Kevlar fiber (0-90°). To study the effect of different reinforcement under load variation on the flexural force of composite materials. Standard ASTM D790 was used to manufacture test samples in ANSYS (13). The theoretical results show that the high flexural strength of epoxy resin with phenol formaldehyde after reinforcement with kefler fibers due to high elasticity coefficient of this fiber will increase with increased fiber ratio.