Cu2ZnGeSe4 (CZGSe) is interesting and promising p-type semiconductor materials for optoelectronics applications and solar cells [1]. In this paper we present reflectivity spectra measured at 300 K in the photon energy range of 1.5 - 6 eV. CZGSe crystals were grown by onetemperature method. A temperature of furnace was risen at the speed of ~50 K/h up to 1200 K. Directional crystallization of the melt was carried out by decreasing the temperature of the furnace at the speed of ~2 K/h down to ~1020 K; homogenizing annealing of the obtained ingots was carried out at this temperature for 300 h. The composition of the crystals was determined by the energy dispersive X-ray micro-analysis (EDAX). The average atomic ratio of Cu:Zn:Ge:Se was found to be close to stoichiometry. The reflectivity is measured using two-beam spectrometer Specord M-40.figureFig.1. Reflectivity spectra (R), the extinction coefficient (K) and phase of reflected ray (ф) vs energy. The Cu2ZnGeSe4 crystals show well pronounced structures of the reflectivity spectra in the range of E ≥ Eg at 300 K as presented in Fig. 1. Up to 12 peaks are observed. The spectral dependences of the real ε1 and imaginary ε2 component of the complex dielectric function ε(E) = ε1(E) + i×ε2(E), the complex refractive index, extinction coefficient and absorption coefficients of CZGSe crystals has been calculated. The energy band structure of Cu2ZnGeSe4 at photon energies higher than the fundamental band gap is derived from the analysis of the structures observed in ε(E) spectra. Financial supports from IRSES PVICOKEST – 269167 and from BMBF MDA11\002 projects are acknowledged. [1] H. Matsushita, T. Ochiai , A. Katsui. J. Cryst. Growth 275 (2005) e995.