It is the hotspot that how to quantitatively partitioning impacts of climate change on wetlands ecosystems. Based on data set of areas of mires, geographical locations, climate parameters collected from the bookMires of China, a model was established to reveal relationships between mire areas and climate and environmental parameters. The results indicated that water-thermal spatial allocations and altitude were the two predominant determining mire areas in China. When applied this model to the Sanjiang Plain, the results implied that climate had a positive effects on mire areas increasing. Climate change in the Sanjiang Plain accounted for 17%-30% of total area change of mires in this zone. Non-climate variables were the main reasons causing decrease of mire areas, occupying -82% to -70.1% of total area change.