The reduction in the amplitude of diurnal temperature (ADT) caused by global climate change will have a profound effect on the carbon balance of alpine ecosystems. Based on CO₂ fluxes measured using the eddy covariance technique, we analyzed the relationship between ADT and CO₂ fluxes over an alpine shrubland on the Qinghai-Tibetan Plateau during different months of the growing season from 2003 to 2016. The results showed that the maximum temperature (MaxTa) and minimum temperature (MinTa) exhibited a single peaked trend that first increased and then decreased, whereas ADT failed to exhibit an obvious trend during the growing season from 2003 to 2016. Daily gross primary productivity (GPP) and ecosystem respiration (Re) exhibited a single peaked trend that increased and then decreased, whereas daily net ecosystem CO₂ exchange (NEE) showed a v-shaped trend. The alpine shrubland ecosystem is a carbon sink during the growing season, and the seasonal NEE, GPP, and Re were (-161.2 ±30.1), (501.9 ±60.2), (340.7 ±54.4) gCm^-2, respectively. During each month of the growing season (June-September) in the alpine shrubland, MaxTa, MinTa, and ADT were the main control factors for daily GPP (P<0.001), Re (P<0.001), and NEE (P<0.01), respectively. The increase in ADT is beneficial to carbon sequestration of the alpine shrubland ecosystem. The results suggest that the decrease in ADT in the future will cripple the carbon sink of the alpine shrubland ecosystem on the Qinghai-Tibetan Plateau.