A pultrusion processing method for long fiber-reinforced nylon which combines the nylon anionic ring-opening polymerization technology and the pultrusion processing method to manufacture long fiber-reinforced thermoplastic nylon composites. The method comprises the steps of forming an active caprolactam sodium salt catalyst composition by reacting melt nylon 6 monomer raw material, i.e., caprolactum, with sodium hydride, forming co-catalyst composition by melting caprolactam and a polymeric co-catalyst, then mixing the active caprolactum sodium salt catalyst composition and the co-catalyst composition in a continuous mixing device to obtain a reaction mixture with low viscosity. The mixture is then charged into a closed impregnating tank to impregnate preheated and dried reinforced fiber, which is immediately pulled into a hot mold for composite molding processing to form a finished product of long fiber-reinforced nylon composites.