Abstract: This study aimed to systematically quantify the sensitivity of the hydraulic performance of labyrinth path irrigation emitters to manufacturing deviations in key geometric parameters. Furthermore, the research sought to reveal the underlying mechanisms of internal flow field evolution caused by these inevitable structural inaccuracies during mass production. Ultimately, the primary objective was to establish a performance-based precision grading control scheme to guide mold manufacturing and injection molding processes, thereby resolving the critical industry challenge of balancing hydraulic stability with overall production costs. A numerical simulation approach was employed utilizing Computational Fluid Dynamics technology. Based on a rigorously experimentally validated numerical model, single-factor simulations were conducted on five critical structural parameters of the labyrinth path: path depth, tooth height, tooth bottom distance, tooth angle, and tooth tip fillet radius. To accurately reflect real-world manufacturing inaccuracies, each geometric parameter was independently evaluated across seven distinct deviation levels. The numerical analysis integrated local sensitivity evaluation methods with a detailed microscopic examination of the flow field characteristics, specifically tracking the evolution patterns of vortex structures, velocity distributions, and turbulent kinetic energy. The simulation results demonstrated that manufacturing deviations significantly altered the internal flow dynamics and overall hydraulic characteristics. Microscopic flow field analysis revealed that tooth height and tooth tip fillet radius were the core parameters regulating vortex structures and energy dissipation. Specifically, a negative deviation of 0.05 millimeters in tooth height expanded the near-wall vortex zones, resulting in an 8.91 percent variation in the vortex area ratio, whereas the impact of the tooth angle was negligible at less than 1 percent. Furthermore, deviations in tooth height, tooth bottom distance, and fillet radius notably modified the velocity distribution and local throttling effects. For example, reducing the tooth height by 0.05 millimeters decreased the average velocity by 4.03 percent but expanded the high-speed area by 21.94 percent due to enhanced separation and turbulence. Similarly, reducing the fillet radius by 0.03 millimeters constrained the mainstream area, decreasing the average velocity by 4.68 percent. Regarding energy dissipation, the maximum deviations in tooth height and fillet radius reduced the average turbulent kinetic energy by 9.16 percent and 7.85 percent, respectively. Interestingly, decreasing the tooth height and bottom distance drastically expanded the high turbulent kinetic energy areas by 378.75 percent and 467.28 percent, directly affecting flow uniformity. The comprehensive sensitivity analysis indicated that the flow coefficient was most sensitive to path depth, with a coefficient of 1.17, followed by tooth bottom distance at 0.66. Conversely, the flow regime index was most sensitive to tooth height. Overall, the sensitivity of the flow rate to the geometric parameters, ranked from highest to lowest, was path depth, tooth height, tooth bottom distance, tooth tip fillet radius, and tooth angle. Based on the sensitivity ranking and internal flow characteristics, a precision grading control strategy was proposed to maintain the target flow rate variation within plus or minus 5 percent. Path depth, being highly sensitive, requires strict tolerance control within plus or minus 0.02 millimeters. Tooth height is recommended to be controlled within plus or minus 0.03 millimeters to prevent the severe deterioration of turbulent kinetic energy. The recommended tolerances for tooth bottom distance and fillet radius are plus or minus 0.07 millimeters and plus or minus 0.01 millimeters, respectively. While tooth angle exhibited minimal impact on flow, its tolerance should still consider anti-clogging and structural assembly requirements.