Based on a series of study to improve the electrooptic coefficient (r33) of nonlinear optical polyimides (NLO-PI) containing benzobisthiazole- based chromophores in our lab, this work concentrated on the modification of the benzobisthiazole-based chromophore VIII (r33 = 6.62 pm/V). At first, a hydroxyl-containing polyimide was first synthesized by using dianhydride and diamine as reactants via thermal imidization and the benzobisthiazole-based chromophores were synthesized by using DABDT as the starting monomer. The NLO precursors were obtained by the Mitsunobu reaction via ether linkage between PI and chromophore; it was then cured at 300¢J to result in the final NLO-PI. The benzobisthiazole-based chromophore of VIII was modified with an insertion of the ethoxy group between the NLO moiety and the main PI backbone to get the NLO-V-1. This method makes the chromophore easier to orient under the electric field during poling; thus a higher r33 (7.4 pm/V) is ensured. NLO-V-2 is another modified sample which had a phenyldiazene group inserted into the chromophore of VIII to increase the conjugated length; this results in a red shifts from 390 nm (VIII) to 484 nm in UV-abs spectrum but the r33 (5.8 pm/V) has only a slight improvement.