<p>Forest carbon stocks constitute a vital strategic resource in addressing global climate change, which possesses irreplaceable significance in achieving climate goals and mitigating global warming. This study assessed and analyzed the changes in carbon stocks and their spatial-temporal distribution characteristics from 2002 to 2022 in the forests of the Great Xing’an Mountains region of China. The Geodetector was used for analyzing the influence of natural environmental factors on the spatial-temporal distribution of forest carbon stocks. The research showed that forest carbon stocks in the Great Xing’an Mountains region fluctuated overall, with higher values in the west and lower values in the southeast. The Centre of Gravity trajectory followed a left-tilted “W-shape,” indicating a trend of dispersion, agglomeration, and dispersion. Environmental factors (mean annual temperature, elevation, and soil type) distinctly affected spatial differentiation, with their combined interactions significantly enhancing individual impacts. The study underscored the Great Xing’an Mountains region’s significance in global climate strategies. Though it occupies a small fraction of China’s land area, it is a vital carbon sink with substantial sequestration capacity, critical for climate mitigation. The findings provide targeted evidence for forest management policies.</p>