The linear and nonlinear optical properties of some ferroelectrics (BaTiO3, KNbO3, LiTaO3 and LiNbO3) are studied by density functional theory (DFT) in the local density approximation (LDA) expressions based on first principle calculations without the scissor approximation. Specially, we present calculations of the frequency- dependent complex dielectric function epsilon(omega) and the second harmonic generation response coefficient X-(2) (-2 omega, omega, omega) over a large frequency range in tetragonal and rhombohedral phases. The electronic linear electrooptic susceptibility X-(2) (-omega, omega, 0) is also evaluated below the band gap. These results are based on a series of the LIDA calculation using DFT. Results for X-(2) (-omega, omega, 0) are in agreement with experiment below band gap and those for X-(2) (-2 omega, omega, omega) are compared with experimental data where available.