To address the issues of low mechanization levels and high labor intensity in the fishing process of Litopenaeus vannamei， this paper proposes an optimized structural design for the ground cage used in rail-type fishing systems within greenhouse ponds to enhance fishing efficiency. Electromagnetic coupling technology was employed to achieve automatic attachment and detachment between the fishing module and the rail lifting system. Furthermore， a trapezoidal structural model of the shrimp inlet was constructed using parametric geometric modeling. Building on this， and incorporating the cruising behavior characteristics of Litopenaeus vannamei， a shrimp-structure collision detection model based on a normal vector projection algorithm was established to dynamically simulate and quantitatively analyze the trap entry process. Response surface methodology （RSM） was utilized to systematically investigate the influence mechanisms of key parameters-specifically outer inlet length， sidewall inclination angle， and depth-on harvesting efficiency. The results demonstrated that the model possesses high reliability （R²>0.9）. Analysis of the structural parameters revealed that the outer inlet length and sidewall inclination angle had the most significant impact on harvesting efficiency （P<0.01）. Optimal harvesting efficiency was achieved when the ratio of the outer inlet length to depth was 2.08， and both the sidewall and inner inlet inclination angles were 75°. Field comparative trials indicated that， compared to the original design， the optimized fishing device increased harvesting efficiency by 14.5%， 12.8%， and 14.6% across different operational periods， respectively. The study concludes that the designed umbrella-shaped ground cage satisfies the requirements of facility-based greenhouse pond rail harvesting systems， offering a viable solution to the harvesting challenges in Litopenaeus vannamei aquaculture in terms of technical advancement， economic feasibility， and operational efficiency. This research provides a theoretical basis and technical reference for the structural optimization of fishing gear and the development of automated harvesting systems.