Abstract: Leaf colors, key enzymes of nitrogen metabolism, and chloroplast ultrastructure were studied in excessive application of nitrogen fertilizer cultivation on chimera Hosta ‘Gold standard’. The results showed that: chlorophyll content significantly increased or decreased in yellow or green leaf area of the chimera in the 2 g/kg of urea fertilizer treatment respectively, and leaf of chimera completely turned green within 28 d. Total N content, activities of nitrate reductase (NR) and glutamate dehydrogenase (GDH) of chimera leaf reached to their highest level after 7 days treatment; activities of glutamine synthetase (GS) reached to their highest level after 14 days treatment, and the changing trends of glutamate synthetase (GOGAT) activities was similar to chlorophyll content on chimera leaf. The develepoment of chloroplast ultrastructure, which lacks normal grana stacking, and contains large number of vacuoles was severely inhibited in the yellow leaf area of the chemera. After 28 d fertilization treatments, normal thylakoid lamellar structure was formed in chloroplast of yellow leaf area, which was similar to the chloroplast structure of the green leaf area and leaf of non-chimera Hosta.