Abstract: To study the mechanical properties of double composite steel-concrete beams, two specimens of two-span continuous composite beams were designed and tested under static load, and compared with the results of finite element simulation. The results showed that the bottom concrete slab of the double composite beam could share the pressure of the steel beam, and its combined action was beneficial to the stability of the bottom flange of the steel beam, but it had no effect on the stability of the web. When the composite beam was designed according to the complete shear connection, the influence of interface slip could be neglected. Compared with the normal composite action, the bending stiffness of double composite beam was larger, and the length of the negative bending moment zone could be extended by about 28.3%. Under the same load, the negative bending moment value of double composite beam was lower, which could delay the cracking of upper concrete slab and effectively control the crack width and crack zone range of concrete slab. The length of bottom concrete slab was in accordance with complete shear resistance, the minimum length of connection design can be established without excessive length. The analysis results of ABAQUS finite element model were in good agreement with the test results, which meant the finite element model in this study can accurately simulate. Improving the strength of the bottom concrete slab of the continuous beam under double composite action can effectively improve the bearing capacity and stiffness of composite beam, and bearing capacity is more reasonable.