This paper contains an analysis of cracking propagation mechanism in flexible pavements. Several Anti cracking systems are proposed, glass fibers reinforcing materials is used .Two different reinforcing methodologies are applied; first: modification of the overlay characteristics by adding chopped glass fibers to the Hot Mixture Asphalt (HMA). Second: reinforcing asphalt overlay by glass gride. Theory of fracture mechanics FM has been employed to determine crack growth rates of the suggested anti - cracking overlay systems. Asphalt mixture designing tests, three paints bending tests and fatigue crack propagation tests were carried out. The Critical Stress Intensity Factors Kic ate determined for plain and reinforced asphalt concrete. Depending on the fatigue crack propagation, the crack growth rate is determined for each type of anti - cracking systems, the cracking process is also analyzed. One of the significant points in this study is the attempt to give better understanding of the crack propagation for multilayer asphaltic overlay or what are suggested herein to call Composite Structure Anti Craddng Overlay System. The results indicate that the reinforcing materials improve anticracking characteristics of the asphalt concrete. Composite structure anti - cracking overlay gives a good solution for reflective cracking phenomenon over old cracked pavements.