Abstract: Pot experiment was conducted in greenhouse to determine the effects of boron (B) supply on root growth and B uptake, utilization and its mobilization in oilseed rape (Brassica napus L.)  at seedling stage under different soil water contents The results showed that, with the decrease of soil water content and B application levels, decreases in total root length , root volume, root growth rate and the ratio of root to shoot were observed, both root and shoot dry matter production were inhibited Furthermore, B concentration and B content in shoot were decreased However, B utilization efficiency (BUE) and B mobilization index (BMI) increased as a result of the decreases of soil water content and B application levels Differences in root morphological parameters (including total root length, root volume, root dry matter ,root to shoot ratio and root growth rate) BUE and BMI in oilseed rape cultivars used in this experiment were obvious, that is ,V1 showed larger root system , higher BUE and BMI than V4 under the same conditions It is suggested that root morophology, BUE and B mobility in plant were the major factors responsible for the differences in response of different oilseed rape cultivars to B deficiency