Provenance and family variation of nitrogen fixation ability during the seedling stage of Alnus cremastogrne were discussed. The random complete block design was adopted in the test.The result showed that except the number of nodule, there were significant or very significant differences for index of nitrogen fixation ability among provenances and single trees within provenances during the seedling stage of the alder. The heritabilities of the number of nodule,amount of nodulation,nitrogenase activity and amount of nitrogen fixation were (0.176 0),0.917 2,0.119 9 and 0.189 6,respectively,and it showed the amount of nodulation was genetically highly controlled.The correlation between the index of nitrogen fixation and EGA was significant.