The usage of different concentrations of three gas mixture (carbon dioxide, nitrogen,oxygen) ,and also vacuum conditions and flexible multi-layer films were studied for determination of aerobic bacteria of smoked kutum fish (Rutilus Frisii Kutum) at ambient condition (T= 25 0C). Normal conditions as a control packaging were compared with four types of modified atmosphere packaging: (N270%+CO230%), (N230% + CO270%), (45%CO2+45%N2+10%O2) and vacuum conditions, in this project. These samples(smoked kutum fish) were packaged in 3 kinds of flexible multi-layer films 3-layer (PET(12)/AL(12)/LLD(100)) , 4-layer (PET(12)/AL(7)/PET(12)/LLD(100) ),and 3-layer ( PET(12)/AL(7)/LLD(100)). Packed samples were performed microbial tests (Aerobic bacteria count), in different times during 60 days, with 15 treatment ,3 run, statistical analysis and comparison of data, were done by software SAS (Ver:9/1) and Duncan’s new multiple range test, with confidence level of 95% (P <0.05). The usage of MAP was not adequet for controlling spoilage but the spoilage process was delayed. The shelf life of smoked kutum fishes (according to Aerobic bacteria count) in 4-layer , under conditions 1,2,3 were reported 60,58,45 days and in vacuum conditions were 40 days, in 3-layer (AL:12) , under conditions 1,2,3 and in vacuum conditions were 55,50,40, 35 days, with 3-layer (AL:7),under conditions 1,2,3 were 45,40,35 days and under vacuum conditions were 30 days. Aerobic bacteria count showed that increasing CO2 concentration increased shelf life of smoked fish. According to these results could be concluded the best condition for controlling the growth of Aerobic bacteria belonged to treatment under modified atmosphere CO2 70% as an antibacterial properties of more carbon dioxide in container 4-layer, since steam permeability of 4-layer was less than 3-layer in order to maintain long-term shelf life of smoked kutum Fish.