Genetic identification of the functional genes causing the erect dwarf-type are of great significance in academic study and rapeseed breeding. We previously identified a naturally-occurred dwarf mutant (named DW871) from a single F1 plant by crosses of sterile line 5824 × recovery line 5771R. By making crosses between the homozygous mutant with a homozygous wild-type line, 47 dwarf rods (DR), 47 high rods (HR) and 10 homozygous dwarf rod lines (HDR) were identified for a genetic mapping study. Three bulks were subjected for simplified genome sequencing technology (BSA-seq), in order to achieve the preliminary mapping of the underlying functional genes. A total of 121998 SNPs were detected between 47 dwarves and 47 high-stem mixed gene pools. 1582 SNPs resulting in non-synonymous mutations were located on ChrA10 chromosome, Interval length is 6.39 MB, including 1405 candidate genes . Out of 1752011 SNPs that were obtained between HR and HDR pools 27723 SNPs led to the non-synonymous mutations. A total of 19 candidate loci were mapped on ChrA03, ChrA04, ChrA06, ChrA07, ChrA10 and ChrC03, Interval length is 5.35 Mb ,including 1143 candidate genes. However, these locus showed un-significant associations and need to be further verified. Interestingly, the association region on the ChrA10 chromosome was revealed by cases and a coincidence interval of 1.83 Mb was suggested. As a summary, the qualitative locus controlling the plant height in DW871 was mapped on ChrA10 chromosome, and this result laid a good foundation for the future fine mapping of the functional gene in Brassica napus L.