The preparation conditions of polyimide (PI) asymmetric membranes on the nonwoven fabric have been investigated. The polyimide membranes were prepared by the phase inversion process in water coagulation bath using the casting solutions composed of polyimide, N, N'-dimethylacetamide (DMAc) as a rich solvent and 1, 4-dioxane (DOx) as a poor solvent. The N2 permeability of polyimide membranes showed 10-5-10-9 [mol/ (m2·s·Pa)]. It was found that polyimide membranes can be utilized as a supporting membrane. And, the polyimide membranes prepared from the casting solution of 25wt% polyimide, 56.3wt% DMAc and 18.7wt% dioxane showed high benzene permselectivity (α =30) for the benzene/ cyclohexane (50vol%/50vol%) solution at 30°C on pervaporation.