Abstract: The result showed that effect of inoculation on casuarina seedling with pure culture of Frankia is obvious. Inoculated seedling`s height,basic diameter,number and fresh weight of nodule and biomass were higher than those of the uninoculated seedlings,Among four tested Frankia strains,Br behaves best.Height of seedling inoculated with Br were 3.45 times that of the control, and 2.73 times in basic diameter. Strain P1 was the better one. Effect of inoculation became more significant as time went on. Seedling's height,basic diameter and biomass appeared to be extremely positively correlative with the number and fresh weight of its own nodule.