Abstract: In this study, 300 Brassica napus germplasms collected from both domestic and international sources were planted in two environments. By integrating phenotypic and genotypic data of oleic acid content, genome-wide association analysis was conducted using EMMAX software. The results indicated that the distribution of oleic acid content in the associated populations presented a continuous bimodal pattern and was controlled by two major gene loci. GWAS analysis identified a dominant QTL locus regulating oleic acid content, situated between the 53853975 and 57808820 bases of chromosome C03, with a contribution rate of 62.51%. It was correlated with the SNP marker and peak values of chrC03＿53853975（A/G） and chrC03＿57808820（C/T）, and the SNP molecular marker chrC03＿56392730（G/T） was closely linked. The corresponding base mutation resulted in polymorphism. When the peak SNP allele was TT, the phenotypic effect value of this trait was 57.93%. This study disclosed for the first time the dominant QTL locus of the C03 chromosome and its SNP molecular marker for the oleic acid content trait of glycole-type rapeseed, with a high contribution rate, providing a crucial theoretical basis for the efficient improvement of this trait and marker-assisted selection.