To investigate the mechanisms of floor heave and support methods for large-section inclined shafts in highly expansive and weak rock, a case study was conducted on the main inclined shaft of a mine in the Yaojie Coal and Electricity Group. Through field surveys and laboratory tests, characteristics such as low rock mass strength, poor integrity, high clay content, and softening and swelling upon water exposure were identified. A Flac3D numerical model was established to simulate the deformation patterns of the tunnel under actual engineering conditions, elucidating the mechanisms of floor heave deformation in large-section soft rock inclined shafts. Three optimized prevention strategies were summarized, and an optimized support scheme of "inverse floor arch and anchor cable" was proposed based on the original support design. Field measurement data indicated that the optimized support scheme significantly improved the floor heave control in soft rock tunnels, enhanced the bearing capacity of the surrounding rock, reduced floor heave deformation, and achieved stability control of the tunnel surrounding rock. This provides an important reference for the control of floor heave in large-section shallow soft rock inclined shafts.