Abstract: As the substrate of photosynthesis, carbon dioxide concentrations play an important role in plant growth and accumulation and distribution of photosynthate. In recent years, atmospheric carbon dioxide concentration is rising and is predicted to continue to rise in the future. The impact of atmospheric CO₂ concentration enrichment on plant has become a research hotspot. Lycium barbarum is one of Ningxia important economic tree species, and the Lycium barbarum industry development will increase farmers′ income. In this research, we studied differences of accumulation and distribution of photosynthate in different organs of Lycium barbarum with two levels, one is doubled CO₂ concentration((720±20) μmol/mol) and another one is natural environment of atmospheric CO₂ concentration((360±20) μmol/mol). The field-based open top chambers system was used to simulate the CO₂ concentration with two standards, and carbon isotope(¹³C) tracer technique was used to trace the destination of photosynthetic product. The photosynthetic parameter was measured in two Lycium barbarum growth stage to determine difference photosynthetic ability between treated trees and a control, and the value of ¹³C was also measured to indicate the influence of doubled CO₂ concentration on accumulation of photosynthate in Lycium barbarum. The results showed that the photosynthetic parameters included net photosynthetic rate, intercellular CO₂ concentration, stomatal conductance and water use efficiency of Lycium barbarum under doubled CO₂ concentration rose significantly compared with those parameters of the control. The leaf transpiration rate under doubled CO₂ concentration in rapid growth stage(90 d) was significantly lower than the control, but no difference in later stage of growth(120 d). Compared with the control, the ¹³C natural abundance of all the four different organs(root, stem, leaf and fruit) of Lycium barbarum of the doubled CO₂ concentration treatment was decreased. After ¹³C isotope labeling, and compared the δ¹³C value of the four different measurement times, the maximum δ¹³C value of leaf was at the 24 h; the maximum δ¹³C value of root and stem was at the 48 h, and then decreased, but the decrease range of root was smaller than stem. Through the change regularity of these organs′ δ¹³C value, it can be confirmed that the transfer direction of photosynthetic product was from leaf to stem, then to root. After been treated with doubled CO₂ concentration, the δ¹³C value in the root, stem and leaf of Lycium barbarum in 90 d and 120 d increased with different degree compared with the control. The percentage of δ¹³C value increased with stem (65.53%)>root (27.39%)>leaf (18.05%) at 90 d, with fruit (145.04%)>leaf (143.56%)>root (49.96%)>stem (43.26) at 120 d. It indicated that, with atmospheric carbon dioxide concentration doubled, the photosynthetic capacity of Lycium barbarum and the accumulation of photosynthate in all four different organs of Lycium barbarum increased, and the accumulation of photosynthate increased in stems in the rapid growth stage was the larger than leaf and root, while the accumulation of photosynthate increased in fruit and leaf was larger in later growth stage.