A study in order to evulated to do the effects of different levels of organic carbon supplement on biofloc formation, inorganic nitrogen and phosphat situation, feed efficiency and growth performance of common carp (Cyprinus carpio) in biofloc system for 42 days. After of acclimatization period, 180 common carp fingerlings with (weight average ± SD, 5/78 ± 0/10 g) were stocked in roundel tank with water capacity of 40 l. Determain of C/N different ratios 15:1 (CN-15) and 20:1 (CN-20) were determined by the content of C/N in commercial feed and the amount of carbon in wheat meal that it was daily used to experimental treatments. Wheat meal don’t added to control treatment (≈ C/N ratio, 10:1). Increasing of carbon to nitrogen ratio was increased water quality parameters such as turbidity, total suspended solid (TSS), total dissolve solid (TDS), Biochemical oxygen demand (BOD), alkalinity and nitrat concentration, but it was decreased total ammonia nitrogen (TAN) and phosphat during the experimental period (p<0/05). Water exchange was reduced 50 % in biofloc treatments than control. Growth performance of common carp fingerlings in different treatments indicated that the fingerlings of CN-15 treatment had the highest of body wieght, specific growth rate, protein efficiency rate (PER) and the lowest of feed conversion rate then both of CN-20 and control treatments. The results of this study suggest that carbon to nitrogen ratio 1:15 a positive impact on water quality parameters, improve food consumption and growth performance of common carp in biofloc system and reduces the amount of water Consumption in the system.