This study aimed to compare the microbial diversity in meatballs with or without blown pack spoilage (BPS) to determine the cause of BPS and to assess the synergistic effect of static magnetic field (SMF) and modified atmosphere packaging (MAP) to reduce the phenomenon of BPS. Results showed that the BPS group with a 2.26-fold larger volume and packaging containing 71.85% CO₂ had Klebsiella spp. (46.05%) and Escherichia spp. (39.96%) as the dominant bacteria, which was different from the spoilage group. The results of isolation and identification of strains from the BPS group and their inoculation test confirmed that Klebsiella pneumoniae was the major strain-inducing BPS in meatballs due to its pack-swelling ability. SMF (5 mT) treatment combined with MAP (40%CO₂ + 60%N₂), which did not influence the sensory quality of meatballs, had a significant synergistic effect on preventing the increase in pack volume. Compared with the control group, this synergistic treatment effectively delayed bacterial growth, drop in pH, and the increase of TBARS. The findings of this study will provide further guidance for meatball manufacturers to adopt effective strategies to reduce the BPS of meatballs.