Several NLO-functionalized polyimides were synthesized through novel synthetic pathways and their NLO properties were characterized. For preventing the disadvantage in poly(amic acid) precursor route, the Mitsunobu reaction and alternative synthetic route for NLO polyimides were chosen. The second-order NLO coefficients (chi((2))) of the synthesized polyimides were between 48pm/V and 122pm/V. The thermal stability of nonlinearity characterized showed that all polyimide films retain their NLO activities at temperatures below 100 degrees C.