Abstract: Carbon nanotubes (CNTs) reinforced Al matrix composites were fabricated by spacer-holder method, including in-situ chemical vapor deposition and ball milling process. The mechanical properties and failure mechanisms of the CNTs/Al composite foams were investigated under compression-compression cyclic loading. The results show that the strain-number of cycle curves of the CNTs/Al composite foams is composed of three stages: elastic stage, strain hardening stage and rapid accumulation stage, which is similar to Al foams. Different from Al foams' deformation of layer-by-layer, the main failure modes of CNTs/Al composite foams are the collapse of pores within significant shear deformation bands under fatigue loading and rapid plastic deformation of the specimens. In addition, the fatigue strength of the CNTs/Al composite foams with CNTs content of 2.5wt% and porosity of 60% increases by 92% than Al foams. The CNTs/Al composites exhibit uniform CNTs distribution and good interfacial bonding between CNTs and Al matrix, which guarantees the effective transmission of fatigue loading in the way of shear stress from Al matrix to CNTs, so that the CNTs can give full play to the characteristics of high strength and high toughness, and then improve the fatigue performance.