Gas separation processes using polymeric membranes have been greatly developed during the last few decadesdue to high energy efficiency and economic advantages. To achieve optimum economic performance, gas separation membranesrequired high permeability and selectivity. So, a number of reports examining the various polymeric materials for gasseparation membranes have been published. Among the studied materials, polyimide (PI), which exhibit high permselectivityfor various gas pairs, high chemical resistance, thermal stability, and mechanical strength, have attracted much attention.This paper focuses on the basic principle of gas separation, preparation procedure of membrane along with the recent developmentsand research trends of PI based materials for gas separation.