In steel-concrete composite structures, due to the existence of certain interface slip and web shear deformation, the assumption of flat section is no longer applicable. In order to scientifically study the effects of shear deformation and interface slip on the deflection and interface slip of composite beams, this paper adopts Goodman's assumption and Timoshenko beam's double generalized displacement assumption, introduces the strain relationship of composite beams and element microsegment mechanical equilibrium, and derives the elastic bending differential equation of double inverted T-shaped steel-concrete composite beams considering shear deformation and interface slip. Then based on the equivalent spring model and the equivalent rod spring model, a theoretical calculation formula for the elastic shear stiffness of the embedded web connection is derived. By using the known deformation and constraint conditions of the composite beam, we obtain the analytical solution of deflection and slip of the simply supported composite beam under concentrated load in the span and verify it through the experimental results of four double inverted T-shaped steel-concrete composite beams with different parameters. The results show that the deflection and slip values obtained from theoretical calculations are in good agreement with the measured values, and the correctness of the theoretical calculation formula for the elastic shear stiffness of the embedded web connection is verified. In the deflection deformation of double inverted T-shaped composite beams, the deflection value caused by bending accounts for about 56% of the total deflection, the deflection value caused by interface slip accounts for about 36% of the total deflection, and the deflection value caused by shear deformation accounts for about 8% of the total deflection. This article comprehensively considers the effects of shear deformation and interface slip on the deflection and slip of composite beams, and makes a significant improvement compared to the model structure that does not consider shear deformation and interface slip.