Konjac glucomannan (KGM)-polyvinyl alcohol (PVA) composite membranes were investigated with the aim of proposing an improved caprolactam pervaporation dehydration process. The composite membranes were characterized by FTIR, SEM, XRD and degree of swelling measurements. The effect of the proportion of KGM in the composite membranes on pervaporation performance was studied. The best separation factor was achieved with an appropriate content of KGM. Both too much and too little KGM can lead to a low separation factor. Besides, pervaporation performance data showed that a higher separation factor could result in lower caprolactam concentration and operating temperature. Evaluation results indicated that the separation performances of KGM-PVA composite membranes were strongly related to their intrinsic structure and to operating parameters.