Abstract: 【Objective】This study aimed to investigate the inhibitory effects of strain KMMDL313 on plant pathogenic fungi，clarify its taxonomic status，biological characteristics，and optimal fermentation conditions，aiming to provide a theoretical basis for the biocontrol of plant diseases using the strain KMMDL313.【Method】Using the strain KMMDL313 isolated from diseased and deceased houseflies in the earlier stages of the research group as study materials， the inhibitory effects of strain KMMDL313 on 8 tested plant pathogenic fungi were determined by the plate confrontation method； its taxonomic status was determined through morphological observation，physiological and biochemical determination，and 16S rRNA sequence analysis； the hydrophobicity of strain KMMDL313 was determined using xylene as the adhering substrate and its autoaggregation was also measured； its motility was determined by different types of motility media； its biofilm formation ability was determined by the 96-well plate cell culture method and the small test tube method； the fermentation conditions of strain KMMDL313 were optimized through single factor experiment.【Result】The strain KMMDL313 showed good inhibitory effects on the growth of the eight plant pathogenic fungi and the inhibitory rate was above 70.00%. According to morphological observation，physiological and biochemical determination，and 16S rRNA sequence analysis，the strain KMMDL313 was identified as Bacillus velezensis，a hydrophilic strain，the autoaggregation rate within 24 h was 77.55% and it had strong motility and biofilm formation ability. The optimization results of the fermentation conditions of the strain showed that：the optimal medium was YSP medium，the optimal carbon source was sucrose，and the optimal nitrogen source was yeast extract； the optimal fermentation conditions were the liquid volume of 250 mL，Erlenmeyer flask volume of 30 mL，the initial pH being 5，the inoculation amount of 50 μL，the culture temperature of 30 ℃，the rotation speed of 240 r/min，and the fermentation time of 24 h.【Conclusion】This strain KMMDL313 can inhibit the growth of plant pathogenic fungi and shows strong colonization ability，indicating that it has great potential for biocontrol applications. Through the optimized fermentation protocol，the fermentation broth of strain KMMDL313 can be produced rapidly and in large quantities，indicating that this strain has great potential for application in biocontrol of plant diseases.