Abstract: Taking high-protein peanut cultivar KB008, high-fat peanut cultivar Hua17 (H17), and higholeic acid/linoleic acid (O/L) peanut cultivar Nongda818 as test materials, a field experiment was conducted in 2010 and 2011 to study the differences in the contents of protein, fat, and their components of the seed kernels, and the differences in the activities of the carbon and nitrogen metabolism enzymes related to the quality synthesis in the blades. As compared with that of H17 and Nongda818, the seed kernel of KB008 had significantly higher protein content but significantly lower soluble sugar content and O/L ratio, and the contents of the amino acid components, especially glutamic acid and lysine, in the seed kernel of KB008 were significantly higher. During the whole growth period, the activities of nitrate reductase (NR), glutamine synthetase (GS), glutamate dehydrogenase (GDH), glutamate synthase (GOGAT), and glutamate pyruvate transaminase (GPT) in the blades of the three cultivars were in the order of KB008>H17> Nongda818. At pod setting stage, the activities of PEPCase and RuBPCase in the blades of the three cultivars were ranked as KB008>H17> Nongda818. The higher PEPCase and RuBPCase activities of KB008 facilitated the protein synthesis and accumulation. The sucrose synthase (SS) activity in the blades was in the order of H17> Nongda818>KB008. The sucrose phosphate synthase (SPS) activity of KB008’s blades was significantly lower than that of the other two cultivars, while the SPS activity of H17’s blades was still higher even in the 60 days after anthesis, suggesting that the higher activities of SS and SPS in the blades were in favor of the fat formation in peanut seed kernel.