Abstract: ZnSe thin films have been successfully deposited the different temperatures on an FTO substrate by using chemical bath deposition (CBD) technique. The chemical baths include the solutions of zinc acetate, Thiourea, selenium and deionizer water. The deposition parameters such as pH of the bath; deposition time, temperature etc. are optimized. As annealing temperature increased 200 ⁰C, the film was increased due to the coalescence of the nature due to crystalline given by the thermal energy occurring in the heating treatment of the film. The sizes of the grains are noticed to enhance at the same time as the temperature better too without annealing (200nm) and with annealing (1μm) fully covered on the substrate. The proportion of the constituent elements measured for before annealing is lower than the after annealing of FTO substrate. The optical absorbance of thin film samples was measured by DRS-UV spectroscopy within wavelength range of 300-1100 nm. The absorption spectra for the ZnSe thin film are analyzed, before annealing maximum absorption coefficient (k) is 402 cmˉ1 and after annealing maximum absorption (k) is 489 cmˉ1. Using the optical parameter, refractive index (n) of the ZnSe thin film with annealing is determined as 1.76 and without annealing is 2.45, the thickness (t) of the ZnSe thin film with annealing is 249nm and without annealing is 87nm and also found that the optical energy band value before annealing 2.48 eV and after annealing 2.02eV. J-V performance of solar cells is reported. The efficiency of the ZnSe thin film is found to increase compared to the without annealing. It will be identified ZnSe thin film deposited by low cost technique and their physical properties are estimated as a possible mechanism for high efficiency.