In order to explore the stress characteristics of the steel-concrete joint section， an experimental model of the steel-concrete joint section of the main beam with a scale ratio of 1∶3 （long × wide × height： 6.0 m × 1.722 m × 2.0 m）， and the four point bending negative moment bending test was carried out， and the stress condition and force transfer mechanism of the steel-concrete joint section under different load conditions were analyzed and compared， Based on the model test， ABAQUS is used to analyze the steel-concrete joint section. The research results show that under normal loading and over loading conditions， the stress level of each component in the steel-concrete joint section is low， the joint section has strong safety reserves， the bearing capacity of the joint section meets the design requirements， and the common stress performance between the steel box and the concrete is good. The bending moment borne by the steel top plate， bottom plate and UHPC layer of the steel-concrete joint section gradually decreases during the transmission from the steel beam transition section through the pressure bearing plate to the steel-concrete joint section， and the force transmission is smooth. The steel-concrete joint section of the test model is mainly loaded by the bearing plate， and the load sharing proportion is reasonable.