Abstract: 【Objective】This study aimed to screen dark septate endophytic fungi （DSE） with biocontrol effects against bacterial wilt of both tomato and ginger， and to clarify their taxonomic status， thereby providing a theoretical basis for the application of DSE in plant disease biocontrol.【Method】DSE were isolated from the root-zone soil of sugarcane by using eggplant seedling trapping method， and the isolated DSE were used as the test materials. Through determining growth-promoting characteristics of co-culture with tomato seedling on plates and observing root colonization characteristics by microscopy， the DSE that could form mutualistic symbiosis with the host were screened. The biocontrol effects of DSE against bacterial wilt of tomato and ginger were evaluated through greenhouse pot experiments. Based on morphological characteristics and molecular phylogenetic analysis of ITS and 28S rRNA sequences， the DSE strains with ideal control effects were classified and identified.【Result】Six endophytic fungi were isolated from the root-zone soil of sugarcane. Screening results of symbiotic strains of tomato showed that， for tomatoes treated with strains L8 and LC8， their dry weight was significantly higher than that of the control without inoculation with endophytic fungi （CK） （P<0.01， the same below）， while the dry weight of tomatoes treated with strain LC3 showed no significant difference compared to CK （P>0.05， the same below）. Laccophenol cotton blue staining showed that strains L8， LC8， and LC3 colonized tomato seedling roots， and microscopic observation showed that they had typical DSE structures. The pot biocontrol experiment of tomato bacterial wilt showed that the LC3 treatment had the best control effects against the disease， reaching 63.2%， which was significantly higher than that of LC8 （34.2%） and L8 （14.7%）； the incidence of LC3 treatment （33.3%） was significantly lower than that of L8， LC8， and CK. The pot biocontrol experiment of ginger bacterial wilt showed that at 10 and 55 d after pathogen inoculation， the disease index in the LC3 treatment was significantly lower than that in the CK， with control effects of 42.6% and 52.4%， respectively； furthermore， at 55 d after pathogen inoculation， the plant survival rate， plant height， and tiller number in the LC3 treatment were significantly higher than those in the CK. The morphological characteristics of strain LC3 were consistent with Cladophialophora immunda， and the similarities of ITS and 28S rRNA sequences between LC3 and Cladophialophora immunda type strain were 98.1% and 99.7%， respectively. In the phylogenetic tree， LC3 also clustered into a monophyletic clade with five Cladophialophora immunda strains including the type strain.【Conclusion】The symbiotic DSE strain LC3 is Cladophialophora immunda， which shows a good biocontrol potential against bacterial wilt.