Abstract: ×On the basis of variation patterns of genetic structure of populations, the annual growth process was classed into early, intermediate and later three periods in I-69 poplar × Simon poplar and I-69 poplar × Nigra poplar F1 clones. The properties of annual growth of various clones were stimulated by Logistic curve, and the maximum points of growth rate per day and the lengths of fast-growing stage were aslo estimated. On the basis of the degrees in which the early, intermediate and later three periods were covered by the fast-growing stages, the growth patterns of different clones were analysed. The clonal growth curves were approached by cross cut polynomiad and the coefficients β0,β1, β2 which made up the growth curves were tested. The results indicated that the differences of the growth curves of height were significant in whole and stage, these of diameter significant only in stage.