To study the in-plane flexural performance of eccentric rectangular RHS beam-column joints， an in-plane bending test was carried out on the joints. The in-plane flexural capacity and failure modes of eccentric RHS beam-column joints were presented. The theoretical formula is improved by finite element parametric analysis， and a practical parametric calculation formula of the in-plane bending capacity of joints is established combined with regressive analysis. Results show that the failure mode of the joint is the combination of the yielding of the column flange surface and the buckling of the column web. Stiffeners can effectively improve the in-plane flexural capacity of eccentric RHS beam-column joints. Parametric analysis was carried out based on the numerical model to study the influence of the beam-to-column depth ratio， the beam-to-column depth-to-width ratio， the column width-to-thickness ratio， and the beam-to-column thickness ratio on the bearing performance of eccentric RHS beam-column joints. Increasing the beam depth and the column thickness is the most effective way to improve the bearing capacity of the joints. Finally， through numerical fitting， the calculation formula of the in-plane flexural capacity of eccentric RHS beam-column joints was obtained. The accuracy of the calculation formula is verified by comparing experimental results with numerical predictions.