This experiment was carried out to evaluate the effect of Suspension on different levels of probiotic Bacillus (Aqua 1 and 2) on the water quality parameters, feed and growth performance and body biochemical compounds of Common carp (Cyprinus carpio) fry in a biofloc system. A total of 450 of fish (with mean initial body weight of 2.09±0.52 g) were divided into five experimental groups (3 replicates each) for 40 days. Experimental diets and biofloc were identical in all, except for the variation in probiotic levels. Two levels of probiotic bacillus and one control was designed which includes; A probiotic was used at 0 (control), Aqua 1: 1.5×10⁸ (T1) and 3×10⁸ (T2), Aqua 2: 1.5×10⁸ (T3) and 3×10⁸ (T4) Inoculation in the culture water. The end of experiment, Mean feed and growth parameters in all probiotic treatments had a significant increase compared to control treatment. The results showed that the highest and lowest final weight was related to T4 (9.31±1.52 g) and control (6.67±0.78 g).  Body composition was measured so that the highest protein content and lowest lipid content were obtained in T1 treatment. Water quality analysis was carried out on days 6, 23 and 40.  At the end of the experiment (day 40), the concentration of ammonia was not significantly different between the control and experimental treatments, while the concentration of nitrate was changed. Based on the results of this study, the probiotic Bacillus at 3×10⁸ in T4 treatment had a positive effect on feed and growth indices of common carp in biofloc system but did not effect on ammonia.