The allocation of net primary productivity (NPP) between aboveground and belowground components (ANPP and BNPP) is essential for comprehending the dynamics of ecosystems processes and functions. In the alpine grasslands on the Qinghai-Tibet Plateau (QTP), the optimal proportion of BNPP (fBNPP) in NPP holds critical importance for productivity dynamics and the rational management of grass resources due to high sensitivity to climate and human-induced changes. However, direct evidence from field research regarding NPP components and fBNPP remains relatively scarce and fragmented. Here, we compiled 704 field observations from the existing studies and published alpine grasslands NPP data to investigate the distribution patterns of NPP allocation and explore the effects of climate and human activities on NPP allocation in the alpine grasslands. Results showed that the alpine grasslands of the QTP had an average fBNPP value of 0.65, with a wide variation ranging from 0.15 to 0.99. Warming and grazing significantly altered the trends of productivity components in response to changes in temperature and precipitation. Our results showed that both warming and grazing increase fBNPP-by 18.01 % under warming and 3.74 % under grazing-through different mechanisms: warming enhanced both ANPP and BNPP, but BNPP showed a greater degree of change. However, grazing reduced both ANPP and BNPP and had a stronger suppressive effect on ANPP. Generally, the spatial fBNPP of alpine grasslands on the QTP exhibited a trend of increasing initially and then decreasing with rising temperatures, differing from the linearly-decreasing pattern on a global scale. Our results emphasized the unique complexity of alpine grasslands NPP allocation on the QTP in response to environmental changes. This study provided significant evidence and theoretical support for the accurate assessment of productivity dynamics and the rational utilization of resources of alpine grasslands.