Methacrylic azopolymers with different spacer lengths in side chains have been synthesized. The spectra and kinetics of the electrooptic effect which arises in azo-polymer films after their irradiation by linearly polarized light are investigated. The photo-induced optical anisotropy in the films appears due to a change of the concentration ratio of trans- and cis-isomers of azobenzene fragments. This explains the nature of the electrooptic effect. Owing to a mobility increment of azobenzene fragments by means of the spacer extension, the electrooptic effect becomes more pronounced, and its relaxation time decreases.