Wetlands play an important role in global carbon and nitrogen cycle. Revealing the spatial differentiation of carbon and nitrogen storage in high-altitude wetlands is helpful to reduce the uncertainty of carbon and nitrogen storage estimation. Relative growth equation method and carbon/nitrogen analyze method were used. The ecosystem carbon and nitrogen stocks (vegetation and soil) and their related environmental factors (water level, soil organic matter, total nitrogen, and total phosphorus, etc.) were measured synchronously in six natural swamp types (tussock swamp-C, reed swamp-L, shrub swamp-G in the lower part of the lake water gradient and larch sphagnum bogs in lower -LNx, middle -LNz and upper -LNs habitats of upper half terrace water gradient) distributed along the water gradient (the water level decreased from 23 cm to -20 cm in the growing season) in Yuelangwan subalpine wetland of Changbai Mountain. It aimed to reveal the spatial differentiation of carbon and nitrogen storage capacity along water gradient and its formation mechanism in high-altitude wetland ecosystems, and explore the coupling relationship of carbon and nitrogen at vegetation, soil and ecosystem scales. The results showed that: (1) vegetation carbon storage (2.95-59.94 t/hm²) and nitrogen storage (0.044-0.733 t/hm²) were constant in the lower part and increased in the upper part along the water gradient, so vegetation carbon and nitrogen were strongly coupled in the horizontal space. (2) Soil carbon storage (252.05-436.86 t/hm²) and nitrogen storage (10.96-18.06 t/hm²) showed a double decreasing pattern or tussock swamp and larch sphagnum bogs in 3 habitats were significantly higher than reed swamp and shrub swamp along the water gradient, so the coupling of soil carbon and nitrogen was weak in horizontal space. However, the coupling of soil carbon and nitrogen storage was relatively strong in vertical space, and there were two types according to whether the vertical change trends of carbon and nitrogen storage were completely consistent (fully coupled type (G and LNz: soil carbon and nitrogen vertical change trends were completely consistent) and fundamentally coupled type (C, L, LNx, LNs: soil carbon and nitrogen vertical change trends were obviously different in the surface layer)). (3) Ecosystem carbon storage (258.35-464.89 t/hm²) and nitrogen storage (11.05-18.21 t/hm²) showed a decreasing pattern in the lower part and a constant pattern in the upper part or tussock swamp and larch sphagnum bogs in 3 habitats were significantly higher than reed swamp and shrub swamp along the water gradient. Therefore, there was a strong coupling of carbon and nitrogen in the ecosystem (complete coupling in the upper part and weak coupling in the lower part). Soil accounted for the majority of carbon and nitrogen storage of the ecosystem, and its proportion decreased along the water gradient (87.13%-99.28% and 95.98%-99.74%), while vegetation only played a secondary role and its proportion increased along the water gradient (0.72%-12.87% and 0.26%-4.02%). (4) The main controlling factors of carbon and nitrogen storage of each component of the ecosystem along the water gradient were different. Carbon and nitrogen storage of vegetation was mainly inhibited by water level, while carbon and nitrogen storage of soil and ecosystem was mainly promoted by soil total phosphorus. Therefore, the ecosystem carbon and nitrogen reserves of Yuelangwan subalpine wetland in Changbai Mountain had obviously spatial differentiation law along the water gradient, and the formation mechanism was that microtopography determined the distribution of plant community types through water redistribution, and then controlled the carbon and nitrogen storage capacity and the coupling of the two. Therefore, the integrity of such environmental gradients should be protected.