Zhengdan958 was used as material to comparatively study the differences in carbon and nitrogen metabolism of summer maize between two types of nitrogen fertilizers, coated urea and urea, in successive two years. The results showed that total sugar content in leaves, sheathes and stems was improved by nitrogen application, and the effect of urea treatment was greater before 12-leaf stage, while that of coated urea (CU) was greater after silking. Nitrogen content in leaves, sheathes and stems was significantly improved by nitrogen application, and the effect of CU was better. Ratio of carbon to nitrogen in sheathes and stems was decreased by nitrogen application, and the effect of CU was greater. Nitrogen harvest index was decreased by nitrogen application, and the decreasing extent in CU treatment was bigger. Translocation of carbon of leaves, sheathes and stems occurred in dough to maturity, and translocation of nitrogen of leaves, sheathes and stems mainly occurred in dough to maturity and silking to dough respectively, and the translocation amounts of carbon and nitrogen in CU treatment were bigger in common. The results showed that CU could improve carbon and nitrogen metabolism of summer maize, which was advantageous to yield increasing.