Small wetlands are an important component of the metropolitan area ecosystem, helping to sustain biodiversity, regulate flood management, and mitigate the heat island effect. This study investigates the Changsha-Zhuzhou-Xiangtan metropolitan area, selects influencing factors from the social and ecological aspects using remote sensing image data from 1992 to 2022, and combines kernel density, standard deviation ellipse, and optimal parameter geographic detector methods to reveal the spatiotemporal dynamic characteristics of small wetlands in metropolitan area ecosystem, as well as their key driving factors. The results show that the small wetlands show a trend of first increasing and then decreasing in time series, and the overall reduction area is about 15.9 km2, of which the loss in urban areas is significantly higher than that in non-urban areas. The distribution of high-density small wetlands in metropolitan area mainly presents a "northwest-southeast" banded pattern along the downstream of the Xiang River main stream and its tributaries. The distribution centroid shifts northeast, and the distribution grows more discontinuous. Against the background of rising temperature and intensified precipitation variability, increased human activity has resulted in the loss of small wetlands. Farmland expansion was the primary driver throughout the early period (1992-2007). In the mid-period (2007-2012), it shifted to a mix of agriculture and development land modifications. In the later period (2012-2022), it became dominated by the increase of construction land, with significant nonlinear strengthening effects among the various aspects. These results provide an objective basis and scientific guidance for small wetlands conservation in the Changsha-Zhuzhou-Xiangtan metropolitan area.