Net ecosystem CO 2 exchange (NEE) over a 5-year-old rubber plantation was measured, using Eddy Covariance technique in 2014 to (1) quantify the seasonal distribution of NEE and its partitioning into daily gross primary production (GPP) and ecosystem respiration (R d) and (2) examine how key environmental factors influence those carbon fluxes. We found that the daily amplitude of carbon fluxes varied substantially within the growing season, with the largest daily changes occurring in July. The daily maximum NEE generally occurred before noon, while maximum R d occurred around sunset. The NEE peak of each growth stage was different. The seasonal variations of NEE, GPP and R d , all of which were closely related to the rubber phenology, reached the peak value in July. Annual NEE, Reco and GPP were 715.21, 591.98, and 1298.93 g C m-2 y-1 , respectively. The 5-year-old rubber plantation behaved as a carbon sink from the end of refoliation stage to the beginning of defoliation period, while it acted as a carbon source within 1-2 weeks. The response of daytime NEE to light (PAR, photosynthetic active radiation) showed that 37-69% of the variation in NEE was explained by the change in net solar radiation. The effect of PAR was dependent on growth stage of rubber plantation. The 3-light response parameters, maximum photosynthetic capacity (P max), ecosystem apparent quantum yield (α) and ecosystem respiration (R d), varied with the growth stage, i.e., initial stage, refoliation, fully expanded leaf and defoliation. Range of P max , α, and R d were −9.44 to −46.61 µmol CO 2 m-2 s-1 , −0.0041 to −0.0428 µmol CO 2 µmol −1 photon, and 1.06-4.91 µmol CO 2 m-2 s-1 , respectively. The highest values of P max occurred in defoliation stage. Both of α and R d were highest in fully expanded leaf stage. The impact of air temperature (Ta) and vapour pressure deficit (VPD) on NEE light response was studied. The magnitude of P max , α, and R d decreased with increasing of Ta. P max increased with the increase in VPD, the maximum value of P max occurred at low level of VPD (VPD 1 kPa). Values of α and R d at medium level of VPD (1 < VPD < 2) were the highest. Multiple linear regression and correlation methods were used to assess the relationship between NEE and environmental factors. The environmental factors controlling NEE were different depending on growth stage.