The polyamideimides having NLO-active chromophores were synthesized by the condensation polymerization of DANS-diamine with trimellitic acid chloride. The polymer was characterized by IR, NMR, UV, DSC, and TGA. The polymer was highly soluble in nonpolar aprotic solvents such as DMF, DMAc, NMP, etc. The polyme was easily spin-coated on a silicon wafer, indium-tinoxide (ITO) coated glass, quartz discs, and NaCl substrates, forming the good quality of thin films. The electro-optic coefficient of r(33) at the wavelength of 1.3 mu m for polymer thin films poled around the glass transition temperature of 142 degrees C measured by simple reflection method was 5.4 pm/V.