In order to explore the effects of nitrogen fertilizer application rate and planting density on the source-sink relationship and yield of sweet potato during ridge-sealing period, and to improve the cultivation techniques of sweet potato in Hainan, a field experiment was carried out from 2019 to 2020. The fresh-eating sweet potato variety Gaoxi14 was used as the test material, and three planting densities were set up, namely 47 600 plants/hm² (D₁), 71, 400 plants/hm² (D₂) and 142 900 plants/hm² (D₃). Four nitrogen application rates (0 kg/hm² (N₀), 60 kg/hm² (N₁), 120 kg/hm² (N₂), 180 kg/hm² (N₃) were designed in a double-factor split plot design with planting density as the main plot and nitrogen application rate as the subplot to study the effects of different planting densities and nitrogen application rates on photosynthetic characteristics, the relative chlorophyll content (SPAD), stem and leaf growth, dry matter accumulation and distribution in source and sink, tuber characteristics in ridge-sealing period, yield and its components and commodity in harvest period of Gaoxi14. Under the same planting density, the net photosynthetic rate (P_n), fresh weight of stem and leaf, number of branches, longest vine length, number of tubers per plant and single tuber weight of commercial sweet potato increased first and then decreased with the increase of nitrogen application rate, and reached the maximum at N₁ treatment. The yield of sweet potato increased first and then decreased with the increase of nitrogen application rate, and reached the maximum under N₂ treatment, which was 32.0% higher than that under N₀ treatment, but there was no significant difference between N₂ and N₁ treatments. Under the same nitrogen application rate, the dry matter distribution ratio of sweet potato roots increased first and then decreased with the increase of planting density. The D₂ treatment reached the maximum but there was no significant difference between D₂ and D₃ treatments. The root shoot ratio and yield increased significantly with the increase of planting density, and reached the maximum at D₃ treatment. The yield of D₃ was 30.9% and 24.1% higher than that of D₁ and D₂, respectively. The results of correlation analysis showed that the nitrogen application rate and planting density had significant effects on the dry matter accumulation and distribution of root tubers, while the planting density had a significant positive correlation with the yield of sweet potato at harvest stage, and the correlation coefficient was 0.704. Based on the results of this experiment, when the nitrogen application rate was 60 kg/hm² and the planting density was 142 900 plants/hm² (D₃N₁), the yield of Gaoxi 14 was the highest, reaching 30.1 t/hm², and the corresponding potato commodity rate was 94.3%, which was the best among all treatments.