Aminopeptidase as a protein hydrolase is widely used in food fermentation and processing. Screening high aminopeptidase-producing strains and studying the enzymatic properties of the flavor enzymes in the strains are important for the development of high-quality soybean product ferments. In this paper， an aminopeptidase-producing strain of Bacillus sp. XYY1 was screened using L-Leu-PNA as substrate in the isolation medium， and identified by morphological observation， physiological and biochemical tests， and 16S rDNA technology， and optimized the enzyme-producing culture conditions by using a one-factor experiment and response surface methodology， and studied the enzymatic properties of the aminopeptidase Lap-Y produced by strain XYY1. The enzyme properties of the aminopeptidase Lap-Y produced by strain XYY1 were investigated. The results showed that strain XYY1 was identified as Bacillus licheniformis， with a starting pH of 6.5， and the content of aminopeptidase was as high as(4，132.75±11.94) U when it was cultured at a constant temperature of 36 ℃ for 35.5 h. The study of the enzymatic properties showed that the relative activity of Lap-Y was highest at the reaction temperature of 55 ℃ with good thermal stability， and that the optimal pH was 9.0， which was good for enzyme stability in the neutral alkaline environment， which was alkaline. The optimum pH value was 9.0， and the enzyme was alkaline in a neutral alkaline environment. Metal ions Mg2+， Fe2+， CO₂+ and Ca2+ could activate the activity of Lap-Y， among which the activation effect of Mg2+ was the most significant for the aminopeptidase Lap-Y when Mg2+ was 1.0 mmol/L， and the activation effect of EDTA， dithiothreitol (DTT) and sodium dodecyl sulphate (SDS) had a stronger inhibitory effect on the activity of Lap-Y. inhibitory effect. The aminopeptidase Lap-Y produced by Bacillus licheniformis XYY1 is suitable for industrialized production and has high application value for food and medical industries.