Abstract: Theoretical analysis and numerical simulation analysis methods was used. A study was conducted on the influence of changes in the structural parameters of the prefabricated beam-column high-strength bolted joint on the flexural capacity of the joint.The influences of parameters such as the thickness of the external diaphragm, the width of the external diaphragm, the arc radius of the external diaphragm and the length of the external diaphragm on the flexural capacity of the joint were studied.The research results show that the numerical calculation results of the finite element have achieved good agreement with the experimental and theoretical analysis results. The flexural capacity of the joint is obviously affected by the thickness of the external diaphragm. As the thickness of the external diaphragm increases, the flexural capacity of the joint increases and the ductility decreases. It is recommended that the thickness of the external diaphragm should not be less than the thickness of the beam flange, but should not exceed the thickness of the beam flange by 2 mm. The width of the external diaphragm is increased, which has a certain strengthening effect on the column joint domain. The width of the external diaphragm is limited to a reasonable range, which is beneficial to improve the flexural capacity of the joint.The flexural capacity of the joint is not significantly affected by the length of the external diaphragm. It is recommended that the length of the external diaphragm can meet the lower limit of the high-strength bolt hole construction requirements. Nodal stress transmission is greatly affected by the arc radius. It is recommended that the ratio of the arc radius to the width of the external diaphragm is about 4 times.