Undergrowth, one important component of the forest ecosystem, plays an important role in maintaining the forest structure and soil quality. The effect of forest at different age on undergrowth has been well documented in a few previous studies. However, those studies, thosen aregarding forest age as time scale tended to neglect the interactions between tree population growth and its undergrowth, thus overlapping inevitably the heterogeneous response of the undergrowth to tree population itself. In this paper, we investigated plant composition, diversity, biomass and nutrient accumulation in the undergrowth of Pinus tabulaeformis forest using a time scale of development rhythm: the height rapid growth, diameter rapid growth, volume slow growth and volume rapid growth. Results showed that it was at the height rapid growth stage when the competition between Pinus tabulaeformis and its undergrowth was severest and abundance, diversity, biomass and nutrient accumulation in the undergrowth were lowest. Therefore, severe thinning should be proposed to be adopted at this stage to relieve the strong competition between them. The slightest competition between Pinus tabulaeformis and its undergrowth occurred at the diameter rapid growth stage, when the aboveground biomass and nutrient accumulation of both the shrub and herb layers reached the maximum and the Gleason, Shannon-wiener and Pielow indices of herb layer have increased from 7817, 2.222 and 0.769 at the height rapid growth stage to 19.978, 3.470 and 0.907 at the diameter rapid growth stage, respectively. Accordingly, forest can be relatively extensively cultivated during this stage. When entered the volume stages, the competition between Pinus tabulaeformis and its undergrowth became daily intensive. The biomass of shrub and herb layer decreased from 2 262.61kg/hm2 and 461.92 kg/hm2 at the former stage to 1 549.85 kg/hm2and 220.84 kg/hm2 at the volume slow growth stage, respectively. While the Gleason and Shannon-wiener indices of the shrub layer increased to the maximum at the stage. Compared with volume slow growth, the diversity indices and nutrient accumulation of both shrub and herb layers were lower at the volume rapid growth stage. While the aboveground biomass in the shrub and herb layers was slightly enhanced further. Moderate thinning or cutting should be taken at the volume rapid growth stage. These results indicated that the development of undergrowth could be regarded as an indicator as growth rhythm of the arbor of pure plantations. And It is of reference values to select forest management ways according to the development of undergrowth.