Abstract: In order to analyse the effects of nitrogen on the nitrogen uptake and nitrate reductase activities of ericoid mycorrhizal fungus, this study determined the mycelial biomass, nitrogen uptake and nitrate reductase activities of three strains of Oidiodendron sp.cultured on ammonium, nitrate and organic nitrogen medium respectively. The results showed that the three strains grew well in different nitrogen source medium, and the strain biomass and nitrogen uptake in inorganic nitrogen medium were significantly higher than that in organic nitrogen medium. The nitrogen uptake by HD19 in nitrate nitrogen medium was significantly greater than that in ammonium nitrogen medium, while the strain ZT13 and D1 had the opposite result. Nitrate reductase activities of the two strains were higher in nitrate nitrogen medium than other nitrogen source. This illustrated that the ericoid mycorrhizal fungi(Oidiodendron sp.)had the ability to utilize different nitrogen source. In all these nitrogen, the nitrate was a good one for ERM fungi growth,and it can also induce nitrate reductase activities of the ERM fungi.