Abstract: 【Objective】 The morphological and agronomic traits of Brassica napus L. under drought stress during pre-flowering and post-flowering stage were studied for screening and identifying species with drought tolerance.【Method】 Principal component analysis, regression analysis and clustering analysis were used to evaluate the drought tolerance of 49 genotypes based on the morphological and agronomic traits under the conditions of normal water supply and drought stress during pre-flowering and post-flowering stage. This included lateral root dry weight, total root dry weight, lateral root volume, total root volume, total root area, plant dry weight, straw dry weight, above-ground fresh weight, stem diameter, number of green leaf, leaf area, plant height, number of primary branches, number of pods per plant, number of seeds per pod, 1000-seeds weight, and yield per plant.【Result】 Principal component analysis reduced the complex interrelationships between all variables to six independent major factors in each treatment. The drought tolerance of Brassica napus L. during pre-flowering and post-flowering had a significant positive correlation (r=0.593**). Forty-nine genotypes were clustered into 3 different levels of tolerance in each treatment. Three, 12 and 34 lines were classified as drought tolerant, medium tolerant and sensitive under drought stress during pre-flowering, respectively, however, 4, 29 and 16 under drought stress during post-flowering, respectively. 【Conclusion】 It is feasible to comprehensively evaluate the drought tolerance of Brassica napus L. at the stage of pre-flowing and post-flowering by principal component analysis, clustering analysis and subordinate function analysis which could be used to screen germplasm lines of Brassica napus L. for drought tolerance．

Key words: Brassica napus L. , drought tolerance , screening and identification , principal component analysis , comprehensive evaluation