Optical properties of densely doped organic optically nonlinear materials were investigated by means of optical absorption spectroscopy, optical harmonics generation, X-ray diffraction spectroscopy and pressure tuning spectroscopy. From the investigation of the absorption λmax, 2‐methyl‐4‐nitroaniline(MNA) in poly methyl methacrylate(PMMA) exhibited an intermediate character between the crystal and the MNA dissolved in the solvents, i.e., some type of “amorphous”, and in the regenerated cellulose(cellophane) almost the same character as the MNA crystal. These results were consistent with the X-ray diffraction analysis, the second and third harmonics generation and the pressure effect on the absorption λmax and fwhm.