Abstract:The present study, a zinc oxide (ZnO) thin films samples prepared using a Chemical bath deposition (CBD). On a glass base where the effect of irradiation with alpha particles on the optical properties of zinc oxide thin films prepared at a concentration of (0.3M) was studied. Irradiation was used from a alpha particle emitted from Americium (Am241) source,with average energy (5.486)MeV. The optical properties of ZnO films measured (200-800nm) using a UV-Vis spectrophotometer.It was to study the relationship of absorbance as a function of photon energy for ZnO thin films.The energy gap for direct transition at standard was also calculated (2.49eV), while at irradiation of 20 min and 80 min, it was (2.37,2.29) eV, respectively. The energy band gap for indirect transfer was also calculated for the standard sample (3.26eV), while irradiation time at (20 and 80) min were (3.20,3.15) eV, respectively.The results for the research have confirmed that the direct and indirect energy gaps decrease with irradiation time when increases the time. The CBD method is used to obtain to ZnO nanotubes, which can be employed as photodetectors.