Abstract: In nursery and glass house,the effects of 23 seedlots of Casuarina equisetifolia and 10 families of C.junghuhniana genotypes on growth and biomass production were studied,and the better mycorrhizal fungus-tree genotype associations were screened out.In nursery trial,results of C.equisetifolia showed that ectomycorrhizal fungus significantly improved seedling growth in diameter and height after inoculating,and that there was genetic variation among seedlots.Some better mycorrhizal fungus-provenance genotype associations were screened out,in the 23 seedlots,seedlot 18357 was the best,and seedlot 18143,18122 and 18121 were better.In glass house trial,results of C.junghuhniana showed that there were significantly differences in growth and biomass production between fungus treatments,families and fungus × family interactions.Inoculation with ectomycorrhizal fungi could improve phosphorus uptake amount in seedling green parts,which increased by 1.3～2.7 times,comparing with uninoculation treatments,and better symbiotic associations in phosphorus uptake were C9216-family No.7 or No.8,E4100-family No.6,No.7 and No.8.By means of multipurpose decision strategy methods,with height,diameter,biomass above ground level and phosphorus uptake in green branches,the 30 associations were ordered in group,the 13 better mycorrhizal fungus-family genotypes were fungus isolate C9216-family No.8,E4100-family No.6,C9216-family No.3,C9216-family No.7,E4100-family No.8,E4100-family No.1,E4100-family No.5,C9216-family No.7,C9216-family No.5,E4100-family No.4,E4100-family No.2,C9216-family No.6 and C9216-family No.10,comparing with the best uninoculating treatment family No.3.And family No.5,No.6,No.7 and No.8 could make better associations with isolate C9216 and E4100,but family No.3,No.1,No.2 and No.10 only made better associations with one of the two isolates.The two trials indicated that ectomycorrhizal fungus inoculation effectiveness existed significantly in genetic variation of provenance and family, which will provide some references in study of casuarina symbiotic genetic improvement.