The responses of aboveground module biomass accumulation and Phyllostachys violascens allometric growth to obtruncation were studied to recommend scientific obtruncation practice. The stem, branch and leaf biomasses of one-year old (1 a) and two-year old (2 a) bamboos either obtruncated or not obtruncated were determined. The allometric growth in biomass was also analyzed. The results showed that obtruncation considerably reduced the stem, branch and leaf biomass of 1 a bamboos. The allocation to stem biomass markedly increased, whereas allocation to branch and leaf biomass decreased considerably. The slopes for the branch and leaf biomass-total biomass of 1 a bamboos significantly increased, whereas the slope for stem biomass decreased. Furthermore, the leaf biomass and its allocation, and the leafing intensity of the bamboos obtruncated at the normal time were all clearly higher than those of the early obtruncated bamboos. The stem, branch and leaf biomass of 2 a bamboos decreased overall after obtruncation, whereas the slopes for branch, stem and leaf biomass-total biomass considerably increased. Furthermore, the leaf biomass of bamboo obtruncated at the normal time was slightly lower than the non-obtruncated bamboos. The leaf biomass allocation and leafing intensity of bamboos obtruncated at the normal time were also higher than those of non-obtruncated and early obtruncated bamboos. All the results indicated that early obtruncation had negative impact on the accumulation of leaf biomass and its allocation, leafing intensity, and biomass allometry. Early obtruncation may also limit the photosynthetic capacity of bamboos. Therefore, early obtruncation is not recommended as a bamboo cultivation practice.