Poled polyureasulfone thin films having excellent transparency from near UV to visible region have been prepared by carrying out additional polymerization of 1,4- phenylene diisocyanate and 4,4'-diaminodiphenyl sulfone simultaneously with poling. The polymerization process is monitored by in-situ second harmonic generation. Under optimal conditions, d<SUB>33</SUB> as large as 8.5 pm/V at a second harmonic wavelength of 532 nm has been obtained. SHG intensity decreased to about 84% of its initial value after having been kept at 100 degrees Celsius for over 1000 hours. Wavelength dispersion measurement of SHG coefficients indicates that d<SUB>33</SUB> of prepared poled films increases by about a factor of three at a second harmonic wavelength of 400 nm.