Abstract: Selecting high-protein peanut cultivar KB008, high-fat cultivar Hua17, and high O/L cultivar Nongda818 as test materials, a field experiment was conducted in 2011 and 2012 to study the effects of foliar spraying paclobutrazol (PBZ) at late flowering stage on the kernel yield and quality and the activities of leaf carbon and nitrogen metabolism enzymes of the cultivars. Spraying PBZ increased the pod yield of the cultivars significantly via increasing the pod number per plant, decreasing the pod number per kilogram, and increasing the percentage of double kernel. Spraying PBZ also increased the kernel fat and soluble sugar contents but decreased the kernel protein content to varying degrees, and increased the O/L ratio of high-fat cultivar Hua17 significantly. PBZ increased the kernel fat content while decreased the kernel protein content of Nongda818 significantly, but had little effects on the kernel protein or fat content of the other two cultivars. Spraying PBZ decreased the leaf nitrate reductase  activity of the three cultivars at their pod setting stage, and the leaf glutamine synthetase  and glutamate dehydrogenase  activities at pod setting and filling stages, with the largest decrement for Nongda818 and the smaller one for KB008 and H17. Spraying PBZ decreased the leaf glutamate oxaloacetic transaminase  and glutamate pyruvate transaminase  activities of the three cultivars at their pod setting and filling stages, illustrating that the decrease of the nitrogen metabolism enzyme activities after spraying PBZ was the main reason of the decreased kernel protein content of the cultivars. PBZ increased the leaf sucrose synthase and sucrose phosphate synthase  activities at pod setting and filling stages, being significant for Nongda818. PBZ improved the leaf phosphoenolpyruvate carboxylase  and ribulose bisphosphate carboxylase activities of the three cultivars at their pod setting and filling stages, being most significant for Nongda818. It was suggested that the increase of the carbon metabolism enzyme activities was the physiological basis of the improvement of kernel fat content after spraying PBZ.