Abstract: Lodging is an important trait that seriously reduces the yield and quality of rapeseed and affects mechanized production. Cultivation and application of rapeseed varieties with strong lodging resistance is an important measure to achieve mechanized production and high yield of rapeseed, and the focus of improving lodging resistance is to improve stem strength. Therefore, a population of recombinant inbred lines (RILs) containing 197 mustard rapeseed lines was used as research materials in this paper. Six characters including stem diameter, Fresh-dry ratio, stem filling degree, stem density, stem bending resistance and stem bending strength were investigated under two environmental conditions in Guiyang and Guiding, respectively. All the characters showed great variation and normal distribution. Correlation analysis under two environmental conditions shows that, there is a highly significant positive correlation between stem plumpness, stem density, and bending strength. Further observation was conducted on the microstructure of the stems of three types of materials with high, medium, and low bending resistance. Compared to low resistance materials, high resistance materials have a larger proportion of cortex, number of vascular bundles, vascular bundle arrangement, and vascular bundle area. In addition, 4 QTLs for stem thickness, 2 QTLs for stem fresh to dry ratio, 2 QTLs for stem plumpness, and 2 QTLs for stem density; four QTLs for stem bending resistance explained the phenotypic variation of 4.1%-5.1%; 10 QTLs for stem strength explained the phenotypic variation of 7.5%-11%. The results of this study can provide basic data information for the cloning of lodging resistance related genes in mustard rapeseed in the future, and are valuable for lodging resistance breeding in rapeseed.