Lactic acid bacteria are an important source of antimicrobial peptides. The aim of this study was to screen antimicrobial peptides with good bacteriostatic activity from peptides derived from the fermentation supernatant of Lactiplantibacillus plantarum LP315 and to analyse their bacteriostatic properties and mechanism of action. The specific methods were firstly， virtual screening of antimicrobial peptides using computer prediction tools and databases， and ADMET prediction for evaluating their safety， followed by synthesis of the screened candidate peptides PLN-1 and PLN-2 using solid phase synthesis method. Then the bacteriostatic properties were analysed by MIC， time-kill curve and protease treatment experiments. Finally， the mechanism of action was investigated by scanning electron microscopy (SEM) and molecular docking experiments. PLN-1 (TELAKKLLVK) and PLN-2 (VVSGHRINGKNQLLISAGLK)， predicted to have good bacteriostatic activity were screened and evaluated as safe and reliable by ADMET. The peptides were chemically synthesised and examined for their antibacterial properties and were found to be inhibitory against S. aureus with a MIC of 5.47 mmol/L for PLN-1 and Escherichia coli with a MIC of 2.97 mmol/L for PLN-2. Both of them showed concentration- and time-dependent antibacterial activity. After partial protease treatment， the antibacterial activity of the peptides was lost， indicating that the antibacterial effect was exerted by the antibacterial peptides. The two peptides were observed to damage the cellular structure of S. aureus and E coil， respectively， by SEM. Molecular docking verified that the two antimicrobial peptides might bind to the peptidoglycan glycosyltransferase/transpeptidase of S. aureus and the lipopolysaccharide structure of E coil， respectively， through hydrogen bond and hydrophobic interactions to exert their antibacterial effects.