Flexible self-supporting TbW₁₀-agarose composite thin films were prepared by combination of Sol-Gel and casting technique based on the functional complementarity between excellent green luminescence polyoxometalates TbW₁₀ and good film-forming matrix agarose. Composition and structure of the films were characterized by FT-IR and Raman spectrum. Thir thickness, surface roughness and microstructure were studied by SEM, AFM and TEM, respectively. And effects of different TbW₁₀ contents on the transmittance and luminescence properties were investigated. On this basis, the reversible chemically responsive luminescent switching performance of TbW₁₀-Agarose green luminescent film was realized under stimulation of HCl and NH₃. The response time and reversibility of chemically responsive luminescent switching performance were studied by fluorescence kinetics curves. And the fluorescence spectrum detection for HCl gas was extended based on the green luminescent thin film sensor with a detection limit of 0.2731 mmol·L ^-1.