Peanut is rich in nutrition, which is a high-quality feed resource and plays an important role in increasing the economic added value of peanut industry. The annual output of peanut seedlings in China is huge. However, there are some problems in the operation of peanut pickers in the main peanut producing areas in China, such as low efficiency and poor reliability in transporting and collecting residual seedlings, which leads to a large number of residual seedlings being left in the fields, which not only wastes resources, but also increases the post-treatment cost. Therefore, it is of great significance to improve the quality and effect of transporting residual seedlings of the pickup harvester for increasing the added value of peanut production. Aiming at the practical problem of peanut seedling waste caused by the lack of efficient and smooth residual seedling conveying and collecting device in peanut picker operation, in order to improve residual seedling conveying efficiency and reduce residual seedling waste, a residual seedling pneumatic conveying device was designed. The working principle of pneumatic conveying device for residual seedlings was expounded, the relationship between equations and key parameters of pneumatic conveying device for residual seedlings was determined, and the influence of conveying airflow and key structure on the speed of residual seedlings was analyzed. Through Box-Behnken experimental design and DEM-CFD gas-solid coupling simulation, the effects of left fan speed, main conveying pipe height and right fan speed on the conveying efficiency of residual seedlings were analyzed. The results showed that the order of influence of conveying efficiency was left fan speed, right fan speed and main conveying pipe height, and the optimal combination was as follows: left fan speed of 1550r/min, right fan speed of 1200r/min and main conveying pipe height of 2.08m. Under the optimal parameter combination, in the main conveying pipe of the pneumatic conveying device for residual seedlings, even mixing and efficient conveying of residual seedlings and airflow can be effectively realized, and the corresponding average conveying efficiencies of Qinghua No.6 and Zhuhua No.2 were 1533.56kg/h and 1451.52kg/h, respectively, which were 9.57% and 8.61% higher than those before optimization.