To study the influence of carbon nanotubes(CNTs) on the mechanical properties and fatigue life on the carbon fiber/epoxy(CF/ER) composites,the static tensile test and tension-tension fatigue test had been carried out in the fiber direction of composites,and the X-ray analysis and SEM observation were used in the present paper.The results show that the addition of CNTs can not affect the mechanical properties of CF/ER composites apparently in the tensile test,but it can improve its fatigue life remarkably.Th...