Abstract: The yam tubers were widely used as the seed potatoes in the cultivation of purple yam in Dehua County, and the quality of seed potatoes could directly affect the quality and yield of purple yam tubers at the latter stage. In order to popularize the high-yield cultivation technologies of purple yam, the effects of different parts of seed potatoes on the plant growth characters and yield of purple yam at the latter stage were studied in Dehua County. The results showed that the purple yam planted with the tubers closer to the top as seed potatoes compared with other parts, the germination period of plant was 8-20 days earlier, the seedling emergence stage was 10-22 days earlier, and the length and width of leaves were respectively increased by 0.2-1.4 cm and 0.1-0.7 cm, as well as the tuber length was 3.5-8.5 cm, the tuber diameter was 0.1-0.6 cm, and the tuber weight and yield per 667 m² were significantly higher than that of other parts (7.06%-25.42% and 7.05%-25.39%). Based on the above analysis, the purple yam planted with the tubers closer to the top as seed potatoes showed early germination and emergence time, strong growth potential and high yield. Therefore, in the production of purple yam, the tubers nearest to the top could be used as the seed potatoes for planting, and the weight of tuber seed potato should be 120 g.