Abstract The numerical values of linear and third order nonlinear optical absorption coefficients and refractive index changes are calculated for several configuration structural parameters and optical intensity. The result shows that in the absence of electric field when the optical incident intensity chosen to be 1MW/cm 2 as asymmetry of the sample decreased the negative values of third order nonlinear absorption coefficient increased and at lower asymmetry the negative maximum value of nonlinear absorption coefficient is seen. Besides, the total absorption coefficient decreased from, because of negative contribution of nonlinear term. In addition, the linear coefficient of refractive index changes becomes decreased while the nonlinear refractive index changes slightly increased in magnitude but in opposite sign to the linear refractive index changes. Consequently, the total refractive index change is further decreased. This result clearly shows that the total refractive index coefficient strongly depends on the nanowire size change. Also, as the incident optical intensity increased from 0 MW/cm 2 to 1.2 MW/cm 2 the total absorption coefficient decreased and the total refractive index changes also decreased. From this result of study the optical absorption coefficient and refractive index changes for ZnO nanowire is strongly depends on both the size and optical intensity of the light. In general since, the size and optical intensity affects the nonlinear term, the material in our cases (ZnO cylindrical nanowire) exhibits nonlinear optical properties.