In PVC/PS pelyblend laminated membranes, perrneabilities were increased as increasing the blend ratio of PS and selectivities were increased with increasing the blend ratio of PVC. The gas permeation mechanism was shifted from the combination of Poiseuille and Knudsen flow model to the solution-diffusion model as decreasing the PS blend ratio. The structure of polyblend laminated membranes showed series model, where PS rich phase was formed at air side and PVC rich phase was at water side. The model of permeation in the polyblend laminated membranes also showed series model structure.