In the paper, the finite element model of the assembled concrete structure is constructed based on the finite element method combined with ABAQUS software, including the specific definition of the model material, the boundary condition and contact setting, the analysis step and loading setting, and the validity of the constructed finite element model is verified. In order to deeply explore the stress changes of the assembled concrete structure, four aspects were analyzed, namely, concrete strength grade, load-mid-span displacement curve, stress of tensile and compressive reinforcement, and stress changes of frame combination beams respectively. The results showed that the larger the concrete strength grade, the relative stiffness ratio at the peak point gradually decreased from 0.44 to 0.27, and the specimen of concrete structure with higher steel content reached the maximum load at the mid-span displacement of 12.5 mm. The reinforcement at the end of the steel frame reaches the yield stress only when the lateral displacement is 25.8 mm, while the RC frame reaches the yield stress when the lateral displacement is 16.1 mm. When the load of the assembled concrete structural frame combination beams does not exceed 0.5 times the ultimate load, the stress change is elastic, which can ensure the stability of the assembled concrete structural building. Using the finite element model to model the assembled concrete structure numerically analyzes its stress change, which can better grasp the development of its structural stress during the actual casting process so as to ensure the safety of the building structure.