Abstract: This paper deals with the structure and properties of short carbon fiber and glass fiber hybrid reinforced Nylon 1010 composites before and after water immersion at 80℃ for 2600 hours.The fibers incoperated in composites were separated and the length of them was measured one by one and then the length distribution was calcufated.The results show that the fibers were shortened considerably during the extrusion process.There is no appreciable difference in the length distribution between carbon fiber and glass fiber.A positive(synergetic) "hybrid effect" can be observed on the mechanical behavior and friction and wear properties of these composites either before and after hot water immersion.Degradation of molecular weight of Nylon 1010 occurs during the hot water immersion and the molecular weight retention decreases with increasing the Volume fraction of glass fiber.The crystallites grew larger during the immersion,however no spherulites can be observed.The retention of mechanical properties of these composites decreases with the increase of Volume fraction of glass fiber.The interfacial adhesion between glass fiber and Nylon 1010 matrix suffers severe damage during hot water immersion and the interfacial shear strength decreases remarkably.However,the interface between carbon fiber and Nylon 1010 matrix remains well bonded after immersion.