A strain of lactic acid bacteria which produce antibacterial active substances was isolated and sifted from Tibetan cheese. After eliminating the interference of organic acids and hydrogen peroxide， the fermentation supernatant of the bacteria still had obvious antibacterial activity. After the fermentation supernatant was treated with pepsin， proteinase K and trypsin， its antibacterial activity was lost， indicating that the antibacterial substance in the metabolite of the bacteria had protein properties， and it was preliminarily determined to be a bacteriocin. It was identified as Lactobacillus plantarum by morphological observation， physiological and biochemical analysis and homology analysis of 16S rDNA gene sequence， named Lactobacillus plantarum ZFM804. The bacteriocin was preliminarily purified by macroporous resin (XAD-16) chromatography， strong cation exchange chromatography and RP-HPLC three-step method. The molecular mass of the bacteriocin was determined 15 ku approximately by SDS-PAGE. The analysis of physical and chemical properties showed that the bacteriocin had good acid-base stability: had bacteriostatic activity in the range of pH 3~11； good thermal stability: 100 ℃ treatment for 30 min still had obvious bacteriostatic activity， and could be degraded by proteases in human body. The results of the antibacterial spectrum assay showed that the bacteriocin had inhibitory effects on both gram-positive and gram-negative bacteria， and was a broad-spectrum bacteriocin.