Abstract:Five grains pure mycorrhizal inoculum of Pisolithus tinctorius (Pt) was injected toeach seeding of Eucalyptus grandis × E. urophylla before transplanting for one month inexperiment plots of Gaofeng Forest Farm near Nanning City, Guangxi. The sustainedeffect of Pt on the increments of plant growth height and tree volume were remarkable,being by 16.34% at the tree age of 3 months and 18.5% at tree age of 16 months,respectively, as compared to the control. The survival rate of seedings after transplanting for 3 months was increased by l5.76％ compared to the control，and the total increments of the tree volume were obvious eigther in young trees or in trees of harvest cutting．The economic profit from the forest would be ten times the cost of mycorrhizal investment.