To investigate the effect of different C/N on the accumulation of off flavor in biofloc reactor, different initial DOC/DIN(Dissolved organic carbon, DOC: Dissolved inorganic nitrogen, DIN)  gradients were set up for group A (no glucose added, C/N of 6), group B (C/N of 10) and group C (C/N of 20) by adding glucose to the bioflocs released from shrimp farming and a 7-day experiment was conducted.Water quality monitoring was carried out everyday. The concentrations of Geosmin (GSM) and 2-Methylisoborneol (2-MIB) in the BFT water were detected at the beginning and end of the experiment and the flocs were taken for nutrient index detection.The results showed that the accumulation of Geosmin (GSM) and 2-Methylisoborneol (2-MIB) was 22.41 ng/L and -0.19 ng/L at C/N of 10, which were significantly lower than those in the C/N of 6 group (76.4 ng/L and 4.43 ng/L) and C/N of 20 group (50.98 ng/L and 3.52 ng/L), respectively; the total ammonia nitrogen and nitrite nitrogen concentrations were lower than 0.10 mg/L and 0.15 mg/L, respectively, in all groups during the experiment; the crude protein content of bioflocs was highest at 31.64 %±0.22 % at C/N of 10. It was shown that the addition of glucose can effectively reduce the accumulation of GSM and 2-MIB production, and the most effective of reducing the accumulation of GSM and 2-MIB production was achieved when the C/N in the biofloc reactor was 10, as well as having water quality improvement effect.