The Eastern Margin Ecotone of Qinghai-Tibet Plateau is recognized both as a crucial ecological function zone and as a carbon pool of China. The assessment and prediction of carbon neutrality in this region are of great significance to the carbon emission control of China and even Asia. The calibrated CASA model was applied to estimate the carbon sink (CS) from 2001 to 2019. Combined with CO₂ emission data acquired from Carbon Emission Accounts & Datasets (CEADs), this paper analyzed the temporal and spatial change of CS and CO₂ emission in the Eastern Margin Ecotone of Qinghai-Tibet Plateau in the past 20 years. STIRPAT and Ridge regression were employed to establish the elasticity between CO₂ emission and six socioeconomic factors:population, secondary and tertiary industries, affluence, urbanization rate and stock farming. Environmental Kuznets Curve (EKC) effect was added to the equation to discuss the reflection on CO₂ emission. Five different scenarios were set up to predict CO₂ emission in 2020-2060. Finally, false-carbon neutrality was proposed and defined, combining the CS data predicted by the GM (1,1) model to study the net carbon sink (NCS) trends and carbon neutrality in the study area. The results show that the CS in the study area has been fluctuating upward about 265 million tons, the highest area is in the southeast region. While CO₂ emission increased rapidly, reaching about 108 million tons in 2019, more than triple the amount in 2001. In the past 20 years, CS was greater than CO₂ emission, but the gap between them has been diminishing. The regression coefficients show that population has the greatest impact on CO₂ emission. For every 1% of population growth, CO₂ emission will increase by about 1.03%. The urbanization rate has an EKC effect in the study area, which means regional CO₂ emission increases firstly and then decreases with the growth of the urbanization rate, and there is no significant EKC effect on affluence. Among the five scenarios, the sustainable (ST) and the baseline (BL) scenarios, the energy-saving (ES) and green development (GD) scenarios will achieve Carbon Emission Peak in 2050 and 2040, respectively. The peak years will gradually shift to an earlier year with the reduction of energy consumption. While the extensive (ETS) scenario will not achieve Carbon Emission Peak before 2060, and CO₂ emission will surpass CS around 2040. In the other four scenarios, CS will always be greater than CO₂ emission during 2020-2060, and net CS will decrease initially and increase afterward. Therefore, due to the extensive development mode, the strong CS capacity of the Eastern Margin Ecotone of Qinghai-Tibet Plateau may be exhausted by the CO₂ emission. We should focus on controlling factors such as population and stock farming, and improve the awareness of energy conservation and emission reduction while planning the development model and protecting the ecology.