In order to improve the working performance of an Alfalfa air conveyor, a type of horizontal screw conveyor with a seed stirring function was designed. The working process of the horizontal screw conveyor was co-simulated by EDEM software and ADAMS software. The effects of a seed stirring mechanism on population movement characteristics, population stress, the seed mass flow rate and the variation coefficient of each index were obtained. The results showed that the stirring mechanism can effectively improve the mobility of the population, reduce the local dead zone of the population, and increase the material filling coefficient between the spiral blades. Under the same working conditions, the horizontal screw conveyor with a stirring mechanism has a higher conveying efficiency and better conveying uniformity. In order to optimize the structure parameters of the Venturi injector diffuser and improve seeding efficiency and uniformity, EDEM software and Fluent software were used to co-simulate the seeding process. The influence of diffuser structure parameters on the working performance of the Venturi injector was analyzed by taking the changes in pressure and velocity in the inner flow field of the pipeline and the velocity and force of seed particles as indices. The results showed that when the diffusion angle is 5°, the length of the diffusion section is 200 mm and the length of the mixing section is 50 mm, the pressure loss of the Venturi ejector is the smallest, the outlet air velocity is the largest, the uniformity of seed feeding is the best and the seed feeding efficiency is the highest. Taking the inlet air pressure and particle feeding efficiency as test factors and the variation number of ejector discharge as test index, a two-factor and five-level full factor test was carried out, and the range and variance analyses were carried out. The results showed that the seed feeding rate and the inlet wind pressure had significant effects on the coefficient of variation. The optimal combination of working parameters was 1.6 kpa inlet wind pressure and 1.8 g/s particle feeding efficiency.