Arbuscular mycorrhizal (AM) fungus (Glomus intraradices) was inoculated to the host plant (Allium fistulosum) and grown in three-part pot culture system, with addition of 4 mmol/L different forms of exogenous nitrogen, 1% glucose and root exudates into the mycelium compartment, effects of glucose and root exudates on the assimilation of different forms of nitrogen and production of arginine by arbuscular mycorrhizal fungus were examined by measuring arginine contents of the extraradical mycelium (ERM) and mycorrhizal roots. The results showed that the absorption capacity of ERM to different forms of exogenous nitrogen and produce arginine is ranked in order of Urea>Gln>NH₄NO₃>Arg/Gly>NH₄Cl>KNO₃; The capability of arginine formation in mycorrhizal roots was ranked in order of Arg>Gln>Urea>NH₄NO₃>Gly>NH₄Cl>KNO₃. Glucose and root exudates increased the dry weight of ERM and spore amount, but reduced arginine concentration in ERM and mycorrhizal roots. These re-sults indicated that the capacity of assimilation of different forms of exogenous nitrogen by AM fungus were different, glucose and root exudates reduced the capacity of assimilation of exogenous nitrogen and production of arginine by AM fungus.