The effect of anisotropic microstructure of a two-dimensional periodic composite on the optical nonlinearity enhancement of the bulk material is investigated. The calculations are based on Stroud-Hui expression for effective third-order nonlinear susceptibility χe and the series expressions of space dependent electric field and/or electric displacement in periodic composite obtained by a simple Fourier approach. The frequency dependences of χe and effective dielectric function ∊e for the anisotropic composites with metallic elliptic inclusions in an insulating host have been evaluated. The results indicate that for geometric anisotropic composites, the positions of the absorption and nonlinearity enhancement are very close, not separate. When the morphology of inclusions varies, the variation tendencies of strengths of the absorption and nonlinearity enhancement are opposite. With the shape variation of elliptic inclusions from prolate to oblate, the nonlinearity enhancement increases while the absorption decreases.