Forest-type changes can have strong impacts on global and local C cycling. Moso bamboo forest is one the dominant forest types in East Asia. The aggressive expansion of Moso bamboo forest into adjacent ecosystems, which might alter the carbon cycling, has been noted recently. Although Moso bamboo has a biennial growth cycle that can cause significant inter-annual variations in net primary productivity (NPP) and net ecosystem productivity (NEP), still few studies have investigated NPP and NEP covering biennial cycles in a Moso bamboo forest with the consideration of above- and below-ground processes. This study clarified the NPP and NEP in a Moso bamboo forest in Taiwan over a 5-year experimental period. During the period, our Moso bamboo forest without intensive management practices showed large inter-annual variations in NPP and NEP (coefficient of variation of 39 and 79%, respectively). The variation mainly owed the inter-annual variations in in above ground NPP. This study confirmed importance of long-term based NPP and NEP estimates in Moso bamboo forests.