The exogenous calcium-induced effects on nitrogen assimilation enzymes and nitrogen use efficiency in wheat seedlings were investigated hydroponically using an ordinary wheat cultivar (Triticum aestivum L. cv. Yumai 34) as the material. Ca2+ treatments with solutions containing 0, 2, 4, and 8 mmol?L-1 Ca2+ were initiated immediately after the complete expansion of the first leaf. Wheat seedlings were sampled five days later to determine the activities of nitrate reductase(NR), glutamine synthetase(GS) and NADH-dependent glutamate dehydrogenase (NADH-GDH) in leaves, as well as the amount of nitrogen assimilation. The results showed that Ca2+ had obvious effects on the ability of nitrogen assimilation in wheat seedlings, and ammonium assimilation enzymes responded variously to different Ca2+ concentrations. Significant increases in NR activity were found in plant leaves exposed to 2 and 4 mmol?L-1 Ca2+ concentrations, among which the former induced the highest activity, whereas 8 mmol?L-1 Ca2+ concentration significantly reduced NR activity. GS activity was markedly increased by 2 mmol?L-1 Ca2+ application, but further increase in the concentration reversed the above effect, even 8 mmol?L-1 Ca2+ induced striking decrease in GS activity. Unlike NR and GS, NADH-GDH activity in leaves manifested pronounced increases with all Ca2+ concentrations in nutrient solution. High nitrogen content in leaves was found always together with Ca2+ concentration of 4 mmol?L-1. All the above results suggested that GS activity was important for nitrogen assimilation, and 4 mmol?L-1 Ca2+ was the most effective concentration to make wheat plants own high ability to assimilate nitrogen.