[Objective] The aim of this paper is to investigate the influences of exogenous 5-aminolevulinic acid （5-aLA） application on the growth and mechanism of winter oilseed rape （Brassica napus L.） before winter. [Method] For this purpose a split-plot experimental design with four treatments of seed soaking with 0,25,50 and 75 mg/L ALA solution （CK,A1,A2 and A3） was carried out from October 2009 to January 2010 in order to observe the influences upon the growth and relevant physiological indexes of Zhongshuang 9. [Result] Seed soaking with ALA solution significantly promotes the growth of double-9 before winter,which is probably due to the fact that ALA application enhances its photosynthesis,absorption of nutrients,and its anti-oxidation abilities. The research also finds that ALA treatment notably increases its photosynthetic pigment contents,root activities,leaf nitrate reductase activities,soluble sugar contents,antioxidase activities,and significantly decreases malondialdehyde（MDA） content. [Conclusion] These results indicate that seed soaking with 50 mg/L ALA solution might have a potential application in increasing the productivity of winter oilseed rape in agricultural management.
