Abstract: Abstract: In order to enhance seeding accuracy and seeding quality of potato, this paper analyses and tests the bouncing and casting process of the cup-belt type potato seed-metering device and the performance of flow deflector. The cup-belt type potato seed-metering devices have the problems such as the nonuniformity of plant spacing, and the higher replay rate and missing rate due to different casting angle, casting speed, casting height and potato bouncing when contacting with furrow. This paper contains the main structure and working principle of cup-belt type potato seed-metering device, and the working principle of the flow deflector is that potato drops out from seed-metering device to the deflector, and then flows along the surface. The flow deflector can reduce longitudinal distance that potato drops into furrow to make the form of potato seed in approximately one column. Flow deflector can also reduce the horizontal velocity of potato seed to decrease the distance of potato dropping into furrow. During the sowing process of seed-metering device, in addition to the contact with the flow deflector, bouncing after contact with soil will also have an influence on seeding results. In the event of seed bounce, the images of bounce process have spatial properties, a circular point uniform density of position of potato in furrow after bounce was formed, each bounce direction has the same possibility after jumping, and the displacement of potato after bounce is inconsistent. The above phenomenon will lead to a higher coefficient of variation for sowing spacing, and a lower qualified rate of seeding. The process of irregular bounce will also increase the replay rate and missing rate. This paper also obtains the main factors that influence bounce distance through the kinematic analysis of casting and bouncing process during potato seeding. The field experiment was carried out; the rotational speed of the driving pulley, the forward speed of the device, and the seed casting height were taken as the experiment factors, and the coefficient of variation of row spacing, the missing rate and the replay rate as the test indices. The test was implemented in Heilongjiang Academy of Agricultural Sciences in September, 2015 and May, 2016. Potato in this test was prepared by Northeast Agricultural University, the shape index of potato was 205.8, and the average mass of potato was 24.38 g. The experimental data were processed and optimized by software Design-Expert 8.0.6. The test result showed the primary and secondary order of influencing factors for each test index. For the coefficient of variation of row spacing, the order was the forward speed of the device, the rotational speed of driving pulley and the casting height of potato seed. For the missing rate, the order was the rotational speed of the driving pulley, the forward speed of the device and the casting height of potato seed. The order for the replay rate was as follows: The rotational speed of the driving pulley, the forward speed of the device and the casting height of potato seed. And results also showed that the coefficient of variation of row spacing was 12.5%, the missing rate was 2.21% and the replay rate was 3.56%, when the rotational speed of driving pulley was 42 r/min, the forward speed of the device was 1.2 m/s and the potato casting height was 640 mm. This device had a good seeding effect compared with the national standards. Through the performance analysis of flow deflector, the theoretical analysis of the casting progress and bouncing process of potato, and the field experiment, it has been verified that the cup-belt type potato seed-metering device which has been optimized can enhance the potato seeding accuracy and sowing effect. This research not only provides the theoretical and technical reference for improvement and optimization of potato seed-metering devices, but also other precision sowing seed-metering devices.