The highly uniform polycrystalline CuIn0.7Ga0.3Se2 (CIGS) thin films for solar cell application were successfully synthesized on the glass substrates using a modified spray process and a continuous flow micro-reactor (CFM) process at low temperature. The as-deposited thin films prepared by each method were annealed under vacuum condition without additional selenization. In order to study the influence of annealing temperature on the properties of the CIGS films, annealing temperature were varied from 200 degrees C to 400 degrees C. The annealing temperature exerted an effect on the properties of the prepared thin films. Based on the XRD measurements, the optimum annealing condition to synthesize the CIGS thin films was 200 degrees C. The crystalline structure of the film annealed at 200 degrees C was in good agreement with the tetragonal structure in the reference. CuIn0.7Ga0.3Se2 thin films were also deposited by a solution-based CFM method and were then thermally treated under the same conditions as the spray. They were compared with the properties of the films deposited by the spray in order to figure out which deposition method is more effective for the synthesis of the CIGS thin films. XRD, SEM, UV-vis, and XPS were employed to study the influence of annealing temperature on the physical properties of the films.