Aiming at promoting the research of mechanical fertilization in potato micro-seed planting, and enhancing the development level of potato industry in China, a kind of fertilizing device corresponding to the former designed potato micro-seed planter was developed. The fertilizing device mainly consisted of a fertilizer box, four fertilizer feeders, eight fertilizer guiding tubes and eight fertilizing openers. Combining with kinematic analysis and discrete element simulation, the whole structure of fertilizer feeder was designed and key parameters were confirmed. The length of spiral blade at single-rotation was 120mm, the outer diameter and pitch of spiral blade was 56mm and 45mm, respectively. The whole structure of fertilizing opener was designed, and parameters of the key parts such as ditching discs and tension spring were determined by theoretic analysis. For ditching discs, the diameter was 350mm, the angle between ditching discs at the place of cluster point was 60°, and the angle between ditching discs was 10°. As indicated in the static experiment of machine, the CV of uniformity of fertilizer discharge was 2.29%. Results showed that fertilizer feeders had good stability for fertilizer discharge. Furthermore, in order to test the performance of the whole fertilizing device, field experiment was conducted. Results showed that the mean horizontal and vertical spacing between fertilizer and potato seeds were 51.2mm and 63.5mm, respectively, which can be confirmed that the overall fertilization performance of the fertilizing device met the agronomic requirements.