Abstract: The objective was to further investigate the differences of varietal characteristics between highproficient nitrogen variety‘Yuyan 9’and low-proficient nitrogen variety‘Zhongyan 100’. Studies on the biological characteristics and nitrogen metabolism of‘Yuyan 9’and‘Zhongyan 100’in seedling stage were carried out. The seedlings of‘Yuyan 9’and‘Zhongyan 100’were cultured by matrix floating, and the biology of leaf and root was investigated. The nitrogen metabolism indices of hydroponic seedlings were detected under different nitrogen concentrations. The results showed that, in seedling stage, significant differences of biological characteristics were observed between‘Yuyan 9’and‘Zhongyan 100’. The total leaf area, dry matter accumulation, root length, root surface area and root volume of‘Yuyan 9’were all significantly higher than those of‘Zhongyan 100’. The nitrate reductase activity (NRA) of leaves was significantly higher than that of veins; compared with low nitrogen condition, the NRA of leaves and veins were both higher in high nitrogen condition; regardless of the leaf parts and nitrogen conditions, the NRA of‘Yuyan 9’was always higher than that of‘Zhongyan 100’. In both high and low nitrogen conditions, the nitrogen concentration and SPAD of ‘Yuyan 9’were both higher than those of‘Zhongyan 100’. These results indicated that the material synthesis and nitrogen accumulation abilities of‘Yuyan 9’were significantly higher than those of‘Zhongyan 100’