Abstract: Public transit-oriented developement is a hot spot in urban construction. The commercial complex over the subway station is one of the key in frastructures, and the design of SRC abnormal joints for the structure cannot be directly guided by JGJ 138-2016. In order to study the failure mode of the SRC abnormal joints and the influence of the variation of beam-column section on its shear capacity, based on the SRC abnormal joints in the conversion layer of a subway vehicle base, a 1/4 scaled abnormal joint was designed and fabricated according to the principle of "strong component, weak joint", and quasi-static loading test was carried out on it. At the same time, taking the relative size of beam-column section as the research parameter, the finite element model of 7 groups of abnormal joints was established and analyzed by ABAQUS program to study the shear mechanism of the core region. The formulae of the shear capacity were proposed and the variation trend of shear capacity of joint core region was explored. The results showed that within the range of SRC beam-column size, increasing the section width of the RC beam and the section height of the RC column were beneficial to the shear performance of the joint core area. When the section width ratio of RC beam to SRC beam was increased from 0.6 to 1.0, the shear capacity of the core area increased by 12%. When the height ratio of the RC column to the SRC column section was increased from 0.5 to 1.0, the shear capacity of the core area increased by 10%. However, increasing the height of the RC beam would cause the concrete strut in the core area to be too steep, which was not conducive to its shear resistance. When the height ratio of RC beam to SRC beam section increased from 0.75 to 1.0, the shear capacity of the core area decreased by 5%.