In our previous study, we have isolated?Lactoplantibacillus plantarum?L3?(GenBank accession No. MT781360) which can secret bacteriocin L3 with broad-spectrum antibacterial activities. This work aimed to illustrate the antibacterial mechanism of bacteriocin L3 and predict the functionalities of the?L. plantarum?L3?strain through whole genome analysis. Preliminary exploration of the bacteriostatic mechanism showed that bacteriocin L3 destroyed the cell membrane integrity and led to the extravasation of the cell contents, leading to cell death. The sequencing results showed that the genome of?Lactobacillus plantarum?L3?was 3 187 020 bp in size, with a GC content of 44.57%. Overall, 3 024 encoding genes were annotated, with a sequence length of 2 679 162 bp, accounting for 84.06% of the total genome length. The strain has strong reproductive and metabolic abilities and high safety. The bacteriocin gene cluster analysis showed that the bacteriocins L3 belonged to the class IIb bacteriocins. This work might provide a theoretical basis for the application of this strain in the food industry, especially its potential use in dairy products.