Abstract: Solution culture to studied the responses of two rape (Brassica napus) cultivars with different boron efficiency to boron-magnesium nutrition at seedling period. The results showed that increasing Mg concentration in the solution had no influence on the growth of two cultivars under lower B level. However, B content and B accumulation in plants decreased, and Mg content, Mg accumulation and chlorophyll content increased. Similarly, increasing B concentration under lower Mg level, Mg content, Mg accumulation and chlorophyll content decreased, the decreasing extent in the B-inefficient cultivar was larger than in the B-efficient cultivar, but chlorophyll content in B-efficient cultivar was larger than in the B-inefficient cultivar. When increasing B concentration in the solution under higher Mg level, there was a significant synergism between B and Mg. The effect of the synergism in the B-inefficient cultivar was less than in B-efficient cultivar. To a large extent, chlorophyll content in plant was tighter relative to Mg content, and less relative to B content. Boron-magnesium nutrition had no significant influence on Zn content. Under the low Mg condition, increasing B concentration could enhance Mn content significantly. At two Mg levels, increasing B concentration improved Fe nutrition of the two cultivars, however, Fe content in B-inefficiency cultivar raised significantly.