【Purposes】 This research is conducted to realize the assembly of steel-concrete composite beams without wet joints, so that the composite beam structure is easy to be disassembled and replaced.【Methods】 ABAQUS analysis saftware was used to study the mechanical properties of high-strength bolted steel-concrete composite beams, an accurate and reliable finite element model was established, and the connection method of precast concrete slabs was improved. On this basis, the effects of bolt pre-tightening force, splicing gap, bolt diameter and strength on the stiffness and slip of the composite beam were studied. 【Findings】 The stiffness of the composite beam was improved with the increase of pre-tightening force, and decreased first and then remained unchanged with the increase of splicing gap. The mechanism of the sliding process of steel-concrete interface was analyzed, and the principle of increasing preload to improve the stiffness of the composite beam was clarified. The comparison between the fitting and the test results proves that the upgraded method proposed in this paper is effective and efficient in improving the stiffness and feasibility of the composite beam.