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【Objective】 Pinus tabulaeformis was the main species of the Northwest afforestation. The growth rhythm of nine populations of P. tabulaeformis was studied. 【Method】 The seeding height and ground diameter growth process were fitted using logistic equation. 【Result】 The relationships were significant between height，ground diameter and the logistic equation in P. tabuliformis populations (r > 0. 9). Each population showed the rhythm in ‘slow-fast-slow' for both seedling height and ground diameter， which accorded with the ‘S' growing curve. There existed allometric phenomenon for seedling height and ground diameter，the growth of seeding height entered the fast-growing phase earlier than that of the ground diameter. According to the logistic equation，the growth of P. tabulaeformis populations was divided into three phases： early growth，fast-growing period，growth of late. There were different fast-growing period of time for different populations in seedling height and ground diameter，which were 26 -36 and 26-61 d，respectively. The fast-growing phase accounted for two fifths of the duration of the whole growth process，but the proportion of the growth increment during fast-growing phase were different for each population. The proportion for seedling height varied 48. 53 % to 58. 48 % ，focused on 56. 87 % - 58. 48 % ，and the ground diameter growth focused 57. 59 % - 57. 98 %. There were significant correlations for seedling height and the theory of growth based on the logistic equation. The case was the same for the ground diameter. The correlation coefficients were 0. 9719 and 0. 9899，respectively. The seedling height and ground diameter were correlated significantly with the extreme value K based on the logistic equation, the correlation coefficient were 0. 9173 and 0. 9999 , respectively. 【Conclusion】 The growth increment and divided in different growth stages of Pinus tabulaeformis can be estimated accurately by using the logistic equation. [ABSTRACT FROM AUTHOR]