Abstract: 【Objective】 To investigate the inhibitory effect of volatile substances produced by Streptomyces rochei A144 on Valsa mali under different phases, and to detect and determine the volatile substance with antifungal activity in vitro. 【Methods】 The inhibitory effect of volatile substances of Streptomyces rochei A144 on apple tree rot at different growth stages (0, 10, 20, 25 and 30 d) was determined by plate coupling method, and the content of volatile substances was detected by headspace solid phase microextraction and gas chromatography-tandem mass spectrometry. After that, the volatile substances with good antibacterial activity under liquid and gas treatment were obtained by plate and coating method, respectively. 【Results】 When the growth time was 20 days, the inhibition rate of volatile substances produced by strain A144 was 100%. Strain A144 produced 63 volatile substances after 20 days of growth. When the concentration was 62.50 μL/L, the gas fumigation treatment of guaiacol, 1-octanol and dimethyl trisulfide could still completely inhibit the growth of apple tree rot. After diluting the original solution by 8 times, the liquid treatment of 1-octanol and dimethyl trisulfide with volume fraction of 12.5% could still completely inhibit the growth of apple tree rot. 【Conclusion】 The volatile substances 1-octanol and dimethyl trisulfide have the ability to significantly inhibit the pathogen of apple tree rot, and have the potential to be an important pesticide source of anti-apple tree rot.