【Aim】 Verticillium stem striping of oilseed rape is an emerging disease in Qinghai Province, with symptoms including vascular bundle discoloration of roots, yellow leaves, and even plant death, seriously affecting the yield and quality of oilseed rape. Therefore, clarifying the pathogen of this disease is beneficial for oilseed rape production and disease control. 【Method】 This study isolated pathogen strains from 8 oilseed rape samples with Verticillium stem striping in Qinghai Province by the culture method. Morphological observation, DNA sequence analysis, and pathogenicity tests were carried out to identify the pathogen. 【Result】 Strain LV1314 grew slowly on potato dextrose agar. The colony turned black due to the production of a large number of microsclerotia. The strain produced verticillate conidiophores in whorls of 1-3. Conidia are hyaline and elongate, with the size of (4.50-12.88) μm×(1.91-4.82) μm and the mean length-to-width ratio of 2.81. The microsclerotia showcase the size of (22.26-194.25) μm×(7.66-48.02) μm and the length-to-width ratio ranging from 1.62 to 13.83. Neither chlamydospores nor dormant hyphae were observed. PCR sequencing was conducted for the internal transcribed spacer and actin gene. The phylogenetic analyses showed these isolates belonged to the Verticillium longisporum lineage A1/D1. The pathogenicity test showed that the pathogen infected oilseed rape and caused similar symptoms with field observation. V. longisporum was re-isolated from the discolored stem, which fulfilled Koch's postulates. 【Conclusion】 The causal agent of Verticillium stem striping on oilseed rape in Qinghai, China is V. longisporum lineage A1/D1. To our knowledge, V. longisporum lineage A1/D1 is first reported on oilseed rape in China.