The inhibitory effects of La on the mycelial growth of several soil-borne pathogenic fungi including Rhizoctonia solani, Pythium sp., Fusarium solani, Selerotinia sclerotiorum, and Fusarium oxyspoxum were studied in vitro. The results show that the mycelial growth was inhibited strongly by the La, with EC50 of 130 ∼ 320 mg·L−1 and EC95 of about 550·40007 mg·L−1 respectively. In addition, the morphological toxicity of La was studied by using the scanning electronic microscope. Treated by La, the mycelial growth of pathogenic fungi was significantly restrained, and the morphological characteristics were found to be abnormal, such as increased ramification, malformation, partial swelling and shrinking, and irregularly entangled mycelial block or rhizomorph.