Allochthonous dissolved organic carbon (DOC) is of importance in lake carbon stock, therefore, the contribution and pathways of allochthonous DOC to planktonic crustaceans deserves further study. A controlled experiment was performed through adding glucose labeled with δ¹³C in water from Lake Fuxian. By analyzing the samples of phytoplankton and zooplankton species, quantity and phospholipid fatty acid (PLFA) biomarkers and their carbon stable isotope, the contribution of allochthonous DOC to crustacean zooplankton carbon source was investigated. The results showed that after adding glucose, δ¹³C values of bacteria and planktonic crustaceans(Bosmina) increased rapidly from -16.28‰ to 5408.25‰ and -23.88‰ to 1974.7‰, respectively, whereas the δ¹³C value of chlorophyceae increased from -27.07‰ to 342.44‰. The growth rate showed that bacteria and zooplankton firstly utilized the adding glucose. The δ¹³C values of bacteria, particulate organic matter (POM) and zooplankton increased sharply at the first day, moreover, the δ¹³C value of bacteria is much higher than that of zooplankton and POM. After the first day, δ¹³C values of bacteria and POM decreased, by contrast, zooplankton δ¹³C value increased slowly. This suggests that allochthonous DOC is firstly utilized by bacteria and form cell particles via the metabolism of bacteria. Subsequently, planktonic crustaceans can utilize allochthonous DOC by grazing cell particles.