Abstract: To investigate the influence mechanism of geometric parameter variations of crescent-rib steel bifurcation pipes on the surrounding rock load-bearing ratio and clarify the regulatory effects of key parameters (expansion ratio, rib width ratio, and bifurcation angle), a three-dimensional finite element model was established based on ANSYS, taking a practical project with a main pipe radius of 2.5 m as the research object. Systematic analyses were conducted on the stress evolution of the bifurcation pipe and the variation characteristics of the surrounding rock load-bearing ratio under different geometric configurations. The results indicate that: (1) With an increase in the expansion ratio, the average surrounding rock load-bearing ratio increases gradually but with a small growth rate; simultaneously, the stress at point LB (central section of the rib plate) increases significantly, and the shell stress fluctuates more notably under the open-pipe condition. (2) As the rib width ratio increases, the average surrounding rock load-bearing ratio remains essentially stable, the stress at characteristic points of the pipe shell changes gently, and the stress at point LB decreases significantly—specifically, when the rib width ratio is less than 0.35, the stress reduction rate at point LB is faster. (3) With an increase in the bifurcation angle, the average surrounding rock load-bearing ratio decreases (with a gradually diminishing decrement), the stress at point LB drops significantly, while the stress at most characteristic points of the pipe shell shows an upward trend.