Abstract: In order to provide theoretical basis for genetic variation and selection of Eucalyptus cloeziana F. Muell. families at seedling stage, the growth (tree height and diameter at ground) of E. cloeziana families were investigated. One-year-old E. cloeziana was used to carry out genetic variation, variance, and genetic parameters estimation of seedling height and ground diameter, and superior families were comprehensively selected by the membership function method. The height and diameter at ground of E. cloeziana were significantly different among the families, and the repeatability was between 0.895 and 0.985. The coefficient of variation of height and diameter at ground were 44.01% and 65.96%, respectively. The family heredity and single heredity of height were 0.894 and 1.605, and the family and single heredity of diameter at ground were 0.985 and 2.935, respectively. Correlation analysis results showed that seedling height and ground diameter were negatively correlated, but not significant. The results of general combining ability analysis showed that the families with high general combining ability of different traits had great differences, which was difficult to carry out combined screening and further analysis was needed. There were abundant genetic variations in seedling growth traits of E. cloeziana families, which were under strong genetic control and had good genetic improvement potential. The height and ground diameter of E. cloeziana families were independent and could be individually oriented. Five optimal families (39, 19, 38, 25, and 13) were selected through the membership function method. Family 39 and 19 had extremely high genetic gain of ground diameter, and they could be used as excellent parents and (or) directive breeding materials.