Abstract: The growth performance of middle-aged Alnus cremastogyne was studied, which could provide reference for superior provenances or families selection and genetic improvement of A. cremastogyne. The growth traits of 98 families from 18 provenances of 7-year-old A. cremastogyne were investigated, and the superior provenances and families were selected according to the analysis of genetic variation. The results showed that there were significant and extremely significant difference of growth traits among provenances and families. The phenotypic variation coefficient and genetic variation coefficient were 0.175−0.303 and 0.033−0.369, respectively. The provenance repeatability and family heritability of growth traits were 0.775−0.836 and 0.828−0.867, respectively. Two superior provenances and eight families were selected through comprehensive index method according to the growth traits of tree height, DBH, crown width, and clear bole height. The average genetic gains of tree height, DBH, crown width, and clear bole height of superior provenances were 4.60%, 7.23%, 5.28%, and 14.87%, respectively, while those of superior families were 9.31%, 13.73%, 18.24%, and 28.75%, respectively. The middle-aged A. cremastogyne exhibited a higher selection potential among provenances or families, which would enhance the genetic improvement effects. The selected superior provenances and families were the important propagation materials for short-rotation industrial raw material forest, genetic improvement, and the follow-up research.