Abstract: The joint genetic improvement of the growth, wood properties and stem form with the data of the 12th year of 33 F1 clones of Poplus deltoides (I-69)～P. euramericana(I-45) were studied. Superior clones could be selected from the independent knocking-out selection. The aggregate character was improved with selection index, but the genetic gain of single character with selection index was less than that of single character selection. Selected with the index of volume and wood density, the clones with fast growth and high density were bred,which was the same of 66.7% as that was selected with the independent knocking-out selection. Selection index B and D were the good indexes composed of growth,wood quality and stem form. When selected with index B,whose heritability was 0. 653 5,the genetic gain of wood density was very small,but the genetic gain of volume was 5.14%. However the genetic gain of wood density was 6. 27% and the volume was not decreased at all selected through index D with heritability 0. 702. It was applicable that the aggregate evaluation and directional selection of multi-characters could be done with selection index.