The invention discloses a steel bridge deck pavement modulus testing device based on a digital image. The testing device comprises a model unit, a control unit, a loading unit, a test-piece fixing unit and a digital image collection unit; the model unit comprises a composite beam test-piece, the composite beam test-piece is compositely formed by a T-shaped steel bridge and an asphalt layer locatedat an upper layer of the T-shaped steel bridge; the control unit comprises a computer and a master control box; the loading unit comprises a loading device, and a test-piece pressure head; the test-piece fixing unit comprises a working platform located at the lower side of the test-piece pressure head, an operation platform, a spherical support arranged on the working platform, a first force transmission gasket, and a second fore transmission gasket; the digital image collection unit comprises a CCD camera supported on a bracket, a first illuminating light source and a second illuminating light source; and the composite girder test-piece can be borne on the working platform through the spherical support. The testing device disclosed by the invention can be compatible with various test conditions, the test data is accurate and convenient to use, and a stress state under the actual work can be better simulated.