The grassland, as the primary ecosystem of Sanjiangyuan National Park, is not only the natural habitats for the survival of wild animals, but also the material guarantees for livestock husbandry. Achieving balance between grassland and livestock is crucial for maintaining the ecological function of the Sanjiangyuan grasslands. Over the past two decades, there has been a continuous recovery of the wild animal population in the Sanjiangyuan area, with grazing of livestock and foraging of wild ungulates constitutes the primary utilization of grassland in this region. In this study, we assessed the grazing pressure of ungulates (large wild herbivores and livestock) on grassland in Angsai Township in Lancang River Source Park, Sanjiangyuan National Park. We used the sample belt method to conduct field surveys from 2020 to 2021 and got the population densities of Pseudois nayaur and Cervus albirostris, the main large wild herbivores distributed in Angsai Township. The Maximum Entropy model (MaxEnt) was used to calculate the suitable habitat area of them. In addition, we used a suitable area to calculate the amount of wildlife. And livestock population numbers were based on official data. The actual carrying capacity was represented in standard sheep units converted for both large wild herbivores and livestock according to the agricultural industry standard of China (NY/T635-2015). The grassland forage yield was estimated by a remote sensing-process coupled model, and the theoretical carrying capacity in the term on edible herbage and crude protein was estimated. The grazing pressure index was used to assess the grazing status of ungulates in the region. The results showed the actual carrying capacity was contributed by approximately (0.67±0.35) ×10⁴ standard sheep units for wild animals, and about 12.99 ×10⁴ standard sheep units from the domestic animals. Under reasonable utilization, the theoretical carrying capacity of edible herbage was 13.15×10⁴ standard sheep units, and the theoretical carrying capacity of crude protein of maintaining basic metabolism, maintaining 45 kg standard sheep weight and daily gain 100 g of standard sheep was 41.40×10⁴ standard sheep units, 23.68×10⁴ standard sheep units and 14.64×10⁴ standard sheep units, respectively. The theoretical carrying capacity of edible herbage quantity was lower than that of crude protein in the region. The capacity of edible herbage quantity is more consistent with the ecological protection goal in the National Park. Both yield and crude protein carrying capacities exhibit seasonal variations, being higher in the warm season compared to the cold season. If considering only livestock, the grazing capacity pressure index is 0.9878; however, if both wildlife and livestock are considered, the index becomes (1.0388±0.0510) and wildlife contributes about 5% to the grazing pressure. This study suggested the wildlife population should be calculated in grassland ecological carrying capacity estimation though domestic livestock contributed much more to grazing pressure than wild herbivores. This study has guiding significance for conducting spatio-temporal dynamic assessment of grassland carrying capacity to achieve balanced management of grassland and livestock, and promote the healthy development of grassland system in Sanjiangyuan National Park.