This study aimed to explore the effects of forest gaps on biomass accumulation and allocation inSPh. heterocladaSf.Ssolida, providing theoretical insights for optimizing cultivation and gap management. SNatural stands ofSPh. heterocladaSf.SsolidaSunder secondarySforests ofSCunninghamia lanceolata were studied. The effects of three gap sizes (large gaps: 14.74~16.50 m2, medium gaps: 8.18~9.35 m2, small gaps: 4.14~4.77 m2) on biomass accumulation, allocation patterns, and allometric growth relationships for 1~3-year-old bamboo were analyzed.SBoth bamboo age and gap size significantly influenced biomass accumulation, allocation, and allometric growth relationship. The results showed that total biomass and component biomass increased with the increasing of gap size, and those of medium and small gaps exhibiting significantly lower than large gaps (PS< 0.05). Allocation proportion of culm biomass and allometric exponent for culm–total biomass initially decreased and then increased with gap size increasing. Conversely, allocation proportion of branch and leaf biomass and their allometric exponent (leaf/branch–total biomass) generally showed opposite trends in 2- and 3-year-old bamboos. For 1-year-old bamboo, allocation proportion of branch biomass and allometric exponent for branch–total biomass all decreased, while allocation proportion of leaf biomass and allometric exponent for leaf–total biomass increased.SSPh. heterocladaSf.SsolidaSadapted to heterogeneous habitats caused by different forest gaps by adjusting biomass accumulation and allocation patterns, and their allometric growth relationships. Biomass accumulation efficiency for bamboos under medium and large gaps enhanced significantly, and leaf biomass allocation proportion increased obviously with high productive potential, which were the suitable and optimal forest gaps under C. lanceolata forest for well-growth and high-yield for Ph. heterocladaSf.Ssolida forest.