3,4-Di-(2'-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and condensed with terephthaloyl chloride to yield novel Y-type polyester (4) containing the NLO-chromophores dioxybenzylidenemalononitrile group, which constituted parts of the polymer backbone. Polyester 4 is soluble in common organic solvents such as acetone and dimethylsulfoxide. Polymer 4 showed thermal stability up to 300 degrees C in thermogravimetric analysis with glass- transition temperature (T-g) measured from differential scanning calorimetry around 91 degrees C. The second harmonic generation (SHG) coefficient (d(33)) of poled polymer films at the 1064 nm fundamental wavelength was around 4.39 x 10(-9) esu. The dipole alignment exhibited high thermal stability up to T-g due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.