Membrane flux is applied by the driver and the membrane resistance to joint decision, in which the nature of the film itself will play a decisive role. Flux is not high for many reasons, the temperature resistance of the film itself, the temperature rise resulting in a long chain molecular rearrangement, so that the membrane surface is more compact, resulting in higher temperatures, smaller flat membrane pure water flux. Different thickness, affect the formation of the membrane structure, resulting in different pore diameter, porosity. Stability and performance moisturizing effect of different post-treatment processes, membrane pores. Casting solution formulation is also about the film itself flux.