Aiming at the seeding accuracy reduction caused by stone-induced vibration of flax seed metering devices in Northwest China's arid regions, this study developed a precision seed metering device with a gradually expanding streamlined seed transfer chute and clarified its anti-vibration and seed-guarding mechanisms via theoretical analysis. A coupled DEM-MBD model was established to simulate the seed-soil-device interaction and seed metering behaviour. The NSGA-II algorithm was adopted for multi-objective parameter optimisation to determine the optimal working and structural parameters: a travel speed of 0.90 m & sdot;s-1, a seed inlet length of 5.90 mm, and a cavity depth of 7.50 mm. Based on the optimised parameters, simulation comparative tests under various travel speeds and stone vibration conditions were performed between the proposed device and the conventional structure. The optimised device increased the seeding qualification rate (SQR) by up to 16.07% and reduced the missing seeding rate (MSR) by a maximum of 49.98%, demonstrating significant performance advantages. Field trials were conducted to validate the model accuracy and the optimised device performance. The results showed high consistency between simulated and measured values (RMSE <= 5.00%, R2 >= 0.90). Field testing confirmed an SQR of 89.33%, an MSR of 5.33%, and an over-metered rate (OMR) of 5.34%, fully satisfying precision flax seeding agronomic requirements. This study provides theoretical and technical support for the development of high-precision seeding equipment for small-seed crops under complex arid field conditions.