Abstract: Studies on the shear mechanisms and calculation models of reinforced concrete beams without stirrups have not reached a consensus. The shear bearing capacity calculation methods for beams without stirrups in Chinese and foreign codes were reviewed. Based on the failure mode of slender beams without stirrups under point loads, a novel unified model and a practical model for shear bearing capacity calculation were proposed. Results show that the critical diagonal crack origin location (x_r,u) correlates strongly with the shear span ratio (λ), while the first branch inclination angle (θ₁) shows no correlation with λ but tends to decrease as the mechanical ratio of longitudinal reinforcement (ω_s) increases, approximating 45°. As concrete strength increases, the tensile-compressive biaxial strength correlation curve gradually transitions from convex to concave. Without introducing the size effect adjustment factor (ζ_s), the ratios of test to calculated values (V_c,t/V_c,c) show a clear increasing trend with the effective height of the cross-section (h₀), and this trend is eliminated after considering ζ_s. The unified model presents superior prediction accuracy, with mean and coefficient of variation being 1.171 and 0.273 for all test results, and 1.075 and 0.259 for beams with rectangular cross-sections, respectively. The practical model is more conservative than ACI 318-19, EN 1992-1-1: 2004 & 2023, and MC 2010 (Level II), and is essentially comparable to MC 2010 (Level I). Additionally, the concrete shear contribution model in GB/T 50010−2024 exhibits poor predictive accuracy and tends to be unconservative.