Bitumen derived from oil or natural bitumen that used as a principal element to make pavement and also as an isolator for long time .However this binder has not shown suitably physical and mechanical properties .Also its performance has been involved with many problem, e.g. limited service time due to the weak physical properties .Consequently scientists and engineers are constantly trying to improve the performance of asphalt pavements. Modification of the asphalt binder is one approach taken to improve pavement performance. From the literature review fiber reinforced bituminous mixes has shown mixed results. It was noticed that relatively few published information concerning fiber modified bitumen is available. Most studies that included fibers in asphalt mixtures had a limited number of trials and investigating the effects of fiber modification has been the secondary purpose to the main purpose of the studies,in many cases. In this study, the effect of different parameters such as fiber type and length, fiber mass fraction, mixing temperature and type of bitumen have been investigation on physical and mechanical properties of bitumen-fiber composite. The tests included softening point ,penetration index, in tcase of physical property measurements and ductility as a mechanical test. The result shows that fibers have improved physical and engineering properties of bitumen. Polypropylene and flat polyester resent the best performance of all .Thus it was statistically illustrated that the length of 12 mm and mass fraction of 0/5% have more effect on improvement of bitumen properties. Finally ductility data were correlated with stiffness matrix components, Q ij . The superior correlation values satisfy and suggest the use of this technique to predict mechanical performance of any other fiber.