Based on the biaxial birefringent model,the structural parameters of thin film,including the principal refractive indices N1,N2,N3,the thickness d and the column angle β were determined by fitting the measured transmittance spectra for two polarizations at the normal and oblique incidence. With the glancing angle deposited technique,the sculptured tantalum oxide thin films were deposited by reactive electron beam evaporation. The structural parameters were extracted by fitting the measured spectral transmittance curves at the incident angle of 0,20°,30°,45° and 60° with the simulated annealing algorithm. Besides,the tilted nano-column structure,the thickness and the column angle were obtained with the cross section of thin film,examined with scanning electron microscope. The results show that the structure parameters of sculptured thin film can be extracted from the transmittance spectra.