A stoichiometric mixture of evaporating materials for CuAISe₂ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, CuAlSe₂ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(I00) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were 680℃ and 410℃, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of CuAISe₂ single crystal thin films measured with Hall effect by van der Pauw method are 9.24 × 10^(16) cm^(-3) and 295 cm²N s at 293 K, respectively. The temperature dependence of the energy band gap of the CuAISe₂ obtained from the absorption spectra was well described by the Varshni`s relation, E_(g)(T) = 2.8382 eV - (8.68×10^(-4) eV/K)T²/(T + 155 K). The crystal field and the spin-orbit splitting energies for the valence band of the CuAISe₂ have been estimated to be 0.2026 eV and 0.2165 eV at 10 K, respectively. by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the Aso definitely exists in the Γ_(5) states of the valence band of the CuAISe₂. The three photocurrent peaks observed at 10 K are ascribed to the A_(1-), B_(1-), and C_(1-) exciton peaks for n = 1.