A double truss composite beam is a new structure that connects two single truss composite beams A and B through a transverse connection system. In order to understand the mechanical performance, deformation capacity, failure mechanism and internal force of each member of the composite beam distribution rules, etc. Design and make test specimens. Through static loading test of A beam of test beam, its displacement, longitudinal strain along the cross-section height, longitudinal strain at the top of concrete slab, axial strain of oblique webs, and the axial direction of transverse coupling system were analyzed. Strain changes with load development. The same specimen model was established and processed by ABAQUS finite element analysis software, and the experimental research results were compared to verify the rationality of the model. The research shows that the composite beam has a good bearing capacity and deformation capacity when a single symmetrical load is applied; the failure mode is A-frame bending failure accompanied by punching and shear failure of the tensioned web rod nodes, and B-frame only oblique web rods receive the axis The force has a small effect; the shear lag coefficient reaches its peak at the ribs, indicating that the stress distribution at the beam ribs is the most uneven. The longitudinal influence range of the coefficients is only near the loading point, and the deformation is concentrated in the middle region. In addition to the axial force of the lower chord The bending effect has a greater influence on the force of the rod, which cannot be ignored.