Abstract: The effect of AM fungi on the growth of sweet potato in the pot culture is studied The results show that soil sterilization inhibits the growth of sweet potato by either inoculation or not．The absorption of phosphorus and biomass of plant are significantly increased by inoculating Glomus D1osse,Glomus intraradices，Glomus sp．WUM 26 among which G．m ,G．i are more effective Colonization rate，hyphal density and SDH activity of introduced AM fungi are accordant with their effects on the growth of the sweet potato The hyphal density in soil inoculating G．m is much larger than that in soil inoculating G．i，while that of G．i is much larger than that of G.s．For the non-sterilization treatments，the effect of inoculation is not significant in term of sweet potato biomass，which is probably caused by the presence of propagule of the indigenous AM fungi in the experimental soil．