A novel Y-type polyurethane 4 containing 5-methyl-4-{5-(1,2,2-tricyanovinyl)-2-thiazolylazo}resorcinoxy groups as nonlinear optical (NLO)-chromophores, which constituted parts of the polymer backbones, was prepared and characterized. Polyurethane 4 is soluble in common organic solvents such as acetone and N,N-dimethylformamide. It showed a thermal stability up to 250 degrees C in thermogravimetric analysis thermogram and the glass-transition temperature (T(g)) obtained from differential scanning calorimetry thermogram was around 118 degrees C. The second harmonic generation (SHG) coefficient (d(33)) of poled polymer film at 1560 nm fundamental wavelength was around 8.43 x 10(-9) esu. The dipole alignment exhibited a thermal stability even at 12 degrees C higher than T(g), and there was no SHG decay below 130 degrees C due to the partial main-chain character of the polymer structure, which is acceptable for nonlinear optical device applications.