The antagonism effect of Lactobacillus plantarum DL3 isolated from traditional northeast suan-tsai against Shewanella putrefaciens was studied. Through the analysis of the minimum inhibitory concentration （MIC）， growth curve， cell membrane permeability， ultraviolet absorption material， protein synthesis and other indicators of S. putrefaciens， the antibacterial effects of lactic acid bacteria（LAB） against Gram-negative bacteria were preliminarily investigated. The results showed that the MIC of strain DL3 cell free supernatant （CFS） against S. putrefaciens was 8.0 mg/mL. L. plantarum DL3 CFS was added after S. putrefaciens culturing for 6 h， the steady-state cell growth of the growth curve of test bacteria was only one-half of the control group， and the number of cells decreased by 1.16 lg （CFU/mL）. The conductivity of S. putrefaciens with L. plantarum DL3 CFS was 34.3 ms/cm， and that of the control group was 33.1 ms/cm， and the OD260nm value of the experimental group was 11.95% higher than that of the control group， indicating that the intracellular nucleic acid substance released. SDS-PAGE confirmed that the number of protein bands in S. putrefaciens treated with Lactobacillus plantarum was small and the color was light. Scanning electron microscopy revealed that the cell wall of the S. putrefaciens cells was destroyed and the cytoplasm leaked. L. plantarum DL3 affected the permeability of the cell membrane of the test bacteria， destroyed the integrity of cells， caused leakage of intracellular nucleic acids， and affected the synthesis of bacterial proteins， led to leakage of proteins， caused cell death of S. putrefaciens.