Nonstructural carbohydrate is the main product of photosynthesis and the basis of plant synthesis. The nonstructural carbon content of leaves in different periods represents the characteristics of carbon intake and carbon demand of plants. Therefore, in this study, we took Lycium ruthenicum as the research object, and set four nitrogen and phosphorus applications (N∶P₂O₅=15∶1, based on pure nitrogen, g/plant), which were 13.5 (high fertilizer), 4.5 (medium fertilizer), 1.5 (low fertilizer), and no fertilization as control, to explore the dynamic characteristics of the daily and the growth period of nonstructural carbohydrate content in leaves, and the effect of fertilization on nonstructural carbohydrate content. The results showed that: (1) the nonstructural carbohydrate and its components in leaves showed the daily dynamic change of increasing first and then decreasing, reaching the highest value at 13:00 noon, and the ratio of soluble sugar to starch decreased first and then increased, reaching the lowest value at 13:00 noon. (2) With the change of growth period, the nonstructural carbohydrate and its components in the leaves showed the daily dynamic change of first increased and then decreased, and reached the highest value in the fruit development period (FDP), the ratio of soluble sugar to starch gradually decreased. (3) There was a significant positive correlation between N content and P content (P < 0.01), a significant negative correlation between N content and NSC and S contents (P < 0.05), and a significant negative correlation between P content and S content (P < 0.01). In conclusion, when the ratio of N to P was 15∶1 and the amount of pure N was 1.5 g-13.5 g, the results showed that fertilization could significantly improve the total nonstructural carbohydrate content, soluble sugar content, starch content and the conversion efficiency between soluble sugar and starch, and promoted the consumption of N and P contents. The effect was more significant with the increase of N and P application rate. Therefore, the adaptability of plants to adversity can be strengthened by fertilization to achieve the purpose of ecological restoration in Northwest China.