The alpine grassland is the major land cover on the Qinghai-Tibet Plateau (QTP), which not only supports the livelihoods and livestock production of local herdsmen but also plays an important role in maintaining ecosystem security on the regional scale. As key elements in the system of grassland and human societies, herbivorous livestock has its carbon budget and carbon cycle from grassland to human societies, which are not well quantified at present. This study used the livestock data from the county yearbook to quantify the carbon budget of herbivorous livestock on the QTP from 2000 to 2020. The ratio of carbon intake was quantified based on the available grass yield (GY_A) and net primary productivity (NPP) estimated by remote sensing. The results showed: (1) the multi-year averaged total NPP and GY_A were (153.88±17.96) Tg C/a and (26.40±3.19) Tg C/a from 2000 to 2020, respectively. The carbon intake of herbivorous livestock (IT_C) was (31.08±0.98) Tg C/a (accounting for 118% of total GY_A). (2) The NPP, GY_A, and IT_C of grasslands on the QTP showed a significant increasing trend, but the ratio of IT_C to GY_A showed a significant decreasing trend. Meanwhile, this ratio showed heterogeneity in spatial (such as different grassland types and different regions). (3) About 43% of the total intake was excreted through feces and urine equating to 13.24 Tg C/a, while 12.35 Tg C/a and 0.96 Tg C/a were released through respiration in heat production and CH₄ in belch by herbivorous livestock, respectively. The carbon of 4.53 Tg C/a was finally sequestered in the livestock body and the partial carbon of 0.384 Tg C/a was exported to human society as livestock products. This study quantified the carbon budget and its spatial and temporal dynamics of livestock on the QTP based on the herbivorous physiological metabolism, which is of great significance for grassland management, carbon sequestration in grasslands and global change ecology.