Garlic is a food and medicine Allium crop of Liliaceae.Although it has anti-tumor and bacteriostatic effects，root rot often occurs after continuous planting.The strain DS55-6F was isolated from garlic rotten root samples in Jinxiang county，Jining city，Shandong province.Through ITS，EF-1 and gpd gene molecularl identification and morphological identification，it was confirmed that the strain DS55-6F was Alternaria embellisia.Based on greenhouse experiments，the strain was inoculated to garlic seedlings，and serious root rot occurred in garlic after 40 days.DS55-6F was obtained through re-isolation and identification，which was in line with Koch’s verification test，indicating that Alternaria embellisia DS55-6F was the pathogen of garlic root rot.The growth characteristics were evaluated by four indexes:different temperature，different pH，different carbon sources and different nitrogen sources.The results showed that the strain was most conducive to mycelial growth at 28 ℃，pH 6，the only carbon source was maltose and the only nitrogen source was beef powder，and when the only carbon source was lactose，and the only nitrogen source was ammonium sulfate or ammonium chloride，the mycella grew slowly.