Abstract: This paper is to study the effect of the waterlogging on biomass allocation and allometric pattern of rhizome and root system in Phyllostachys rivalis. The biomass of 1-year-old bamboo rhizome and root was investigated in a pot experiment with treatments of artificial irrigation and waterlogging for three and six months. The response, adaptative strategy of biomass allocation in rhizome and root of Ph. rivalis under long-term waterlogging conditions were analyzed. The results showed that the growth of roots was inhibited under waterlogging conditions and the allocation proportion of Ph. rivalis biomass was in the order of rhizome >root. Compared to the CK, the biomass of root and the ratio of root biomass to total biomass decreased significantly, the ratio of rhizome biomass to total biomass increased in the TR. It would grow lots of rhizome and root with the extension of waterlogging time and the biomass increased significantly. But no obvious impact of waterlogging on the proportion of rhizome biomass, root biomass or waterlogged rhizome in total biomass. The relationship between rhizome biomass and root biomass of Ph. rivalis accorded with positive power function in TR and CK. But the growth index in TR was higher than that in CK. By this research it showed that Ph. rivalis has ecological plasticity and regulatory on material distribution and growth of rhizome and root. And it could adapt to the waterlogging conditions gradually through reasonable distribution of biomass and allometric accommodation. This research could provide references for its application in vegetation restoration of wetland and areas of fluctuating water tables.