997 natural Brassica napus varieties were used to screen rapeseed varieties sensitive to aluminum （Al） and study the tolerance mechanism of rapeseed to Al toxicity. The two-step screening method of soil culture initial screening and nutrient solution culture re-screening was conducted. The aboveground fresh mass and relative root elongation were used as indicators to screen Brassica napus varieties sensitive to aluminum. The physiological mechanism of aluminum tolerance in rapeseed was analyzed. The results showed that 997 natural Brassica napus varieties had significant genotypic differences at the stage of seedling in acidic soil. 142 extreme varieties with different aluminum sensitivity including 77 varieties tolerant to aluminum and 65 varieties sensitive to aluminum were screened. A nutrient solution culture system was used to re-screen the 142 rapeseed varieties under aluminum and no aluminum. The results of cluster analysis showed that 97 varieties exhibited good consistency of growth in two cultivation systems. Two aluminum varieties （806 and 985） tolerant to aluminum and two varieties （482 and 811） sensitive to aluminum were finally determined after multiple repeated phenotypic experiments. The biomass of varieties （482 and 811） sensitive to aluminum under aluminum toxicity decreased by about 45% compared to that under non-aluminum treatment， and root growth was significantly inhibited， while varieties tolerant to aluminum had no significant difference. Compared to varieties sensitive to aluminum， varieties tolerant to aluminum accumulated less aluminum in their roots under aluminum toxicity， had lower levels of reactive oxygen species， and significantly increased the activity of antioxidant enzymes including CAT and POD in their roots compared to that under no aluminum， indicating that it may be one of the important physiological mechanisms of aluminum tolerance in rapeseed.