In order to study the normal section bending capacity and structural requirements of a new type of inverted U-shaped steel-encased concrete composite beam, nonlinear finite element models of the composite continuous beams have been stablished with the reference of the existing U-shaped steel-encased concrete composite continuous test beams, and the load-mid-span deflection curves of the finite element models of the composite continuous beams have been simulated and compared with the related test results. The rationality and effectiveness of the modeling method and parameter selection of the composite beam finite element models are verified. Based on the finite element model of composite continuous beams, the main influencing parameters of bending capacity of inverted steel-encased concrete composite beams are analyzed. Based on the test and simulation results of normal section bending capacity of inverted U-shaped steel-encased concrete composite continuous beams, a simplified plastic theory is proposed to calculate the normal section bending capacity of composite beam, but the plastic theoretical calculation value of the normal section bending capacity of the composite beam should be multiplied by the modified coefficient of 0.96. The comparison between the plastic theoretical calculation value of the normal section bending capacity of the composite beam and the simulation value of the finite element model of the composite beam shows that the two values are very safe and close, and the modified simplified plastic theory calculation value of the normal section bending capacity of the composite beam is accurate and reliable enough.