In modern structural design, box-shaped connections are widely applied in steel structures for the high structural strength, uniform stress distribution, torsional stiffness, and reliable connections. However, traditional connections of rectangular tube columns with internal partition plates and H-beams often exhibit localized stress concentrations, impacting both performance and construction quality. A bidirectionally reinforced T-shaped component joint between rectangular tube columns and H-beams are proposed. Using ABAQUS finite element software, seismic performance analysis was conducted on five groups of reinforced rectangular tube column and H-beam joints under bidirectional cyclic loading. Hysteresis and skeleton curves were obtained, and the effects of factors such as flange width of the steel beam and web length of the T-shaped component on joint performance were explored. Results indicate that increasing the flange width of the beam and the web length of the T-shaped component significantly enhances the joint’s peak load capacity. When the beam flange width is increased from 100 mm to 150 mm, the peak load increases by 27.65%, and when the web length of the T-shaped component is extended from 100 mm to 200 mm, the peak load increases by 16.79%. Plastic hinges were observed to shift to the connection between the T-shaped component and the steel beam flange, establishing an effective energy dissipation mechanism. It is recommended to optimize the shape of the reinforced components on the rectangular tube column-H beam joint, such as by using chamfered edges, to reduce stress concentration and significantly enhance seismic performance.