Sufu, a traditional fermented soybean curd, is prone to contamination by Bacillus cereus. In this study, 133 lactic acid bacteria (LAB) strains were initially screened from spring and winter Mao-tofu samples for their ability to inhibit the growth of B. cereus ATCC 14579T. Among these strains, five Lactococcus lactis strains exhibited a good safety profile and were capable of growing in pH 4–9 and salt concentrations of 6%–8%. Antimicrobial experiments conducted on the B. cereus group from sufu factories showed that L. lactis LJL7m20 strain had the strongest inhibitory effect. Whole-genome sequencing revealed the presence of three genes associated with high osmotic stress response and eight distinct two-component systems that may contribute to the strain's tolerance, enhancing its survival in high-salt environments. The strain was further identified as L. lactis subsp. lactis through a combination of phenotypic and genotypic analysis. Additionally, bacteriocins nisin Z and nisin A/Q were identified using the BAGEL4 and antiSMASH databases. ELISA further confirmed the strain's ability to produce nisin. A fermentation validation study demonstrated that inoculation with the strain contributed to reduce the number of B. cereus group in sufu pehtzes. This study provides a theoretical foundation for the use of new biocontrol bacteria to improve the safety of traditional fermented soybean foods.