In CuGaS2 crystals absorption and luminescence spectra at the temperature 9 К at excitation by different wavelengths of Ar+ laser are investigated. In the luminescence and absorption spectra in crystals CuGaS2 at the temperature 9 K groups of lines having almost hydrogen-like dependences are found. One series of lines (F0,f1f3) is found in the absorption and luminescence spectra. The other series (x1-x5) is present only in the luminescence spectra. In the luminescence spectra of CuGaS2 crystals at 9 K excited by the line 4765Å of Ar+ laser three wide bands of radiation (А, В and С) at the energies 2,3982 eV, 2,3477 eV and 2,3055 eV, correspondingly are found [1-3]. On the top of the most intense band B a narrow line of radiation F0 (2,3964 eV) is found. The radiation bands B, C and D have the half-width being an order higher than the radiation line F0 (Fig.1). The narrow line of radiation has the half-width of 1-2 meV and it is differently shown in different samples. From different technological lots the samples were found wherein the band B had higher intensity than that of the line F0. At strong luminescence in the region of the band B a part of the radiation energy is absorbed in result of electron transitions to the level of the bound exciton F0. In the region of the radiation bands C and D narrow lines of radiation are not observed. In the absorption spectra the absorption band F0 strictly at the energy 2,3964 eV and the absorption bands f1(2,4013 eV), f2 (2,4040 eV) and f3 (2,4071 eV) are found. These lines are very close and are similar to the hydrogen-like series of the bound exciton. The distance between the lines decreases (F0 - f1 = 4,9 meV, f1 – f2 = 3,2 meV and f2 - f3 = 1,8 meV) as the transition energies increase. The found regularities of the luminescence and absorption spectra allow us to consider that they are determined by excitons bound on neutral acceptor. The luminescence excitation is of resonance character. The energy band model explaining electron transitions between the levels of the exciton bound on neutral acceptor is proposed.figuraFig.1 Luminescence spectra of CuGaS2 crystals at 9 K excited by line 5145 Å of argon laser.