The speciation and ecological risk of sediment Hg and As in different water-level gradients of the Grus nigricollis habitat in Lake Caohai wetland, Guizhou Province were analyzed by modified Tessier sequential extraction. The results showed that Hg content in sediments ranged from 0.45 to 1.51 mg/kg. In terms of speciation composition, residual Hg > Organic Matter Hg > Carbonates Hg > Fe-Mn Oxides Hg > Exchangeable Hg. The content exceeds the soil environmental quality risk control standard for soil contamination of agricultural land and is related to the regional geological background and human activities. There is no regularity in the content distribution on the water level gradient. The ratio of non-residue Hg in Liujiaxiang (zone A) and Huyelin (zone C) area increased with the water level gradient, while the non-residue Hg in Zhujiawan (zone B) showed a downward trend. The As content is between 16.4 and 23.8 mg/kg, and speciation distribution residual As > Organic Matter As > Fe-Mn Oxides As > Carbonates As > Exchangeable As. The As content is equal to the land background value of Guizhou Province. With the water level gradient rises, the total content increases, the proportion of residual increases gradually, and the nature gradually stabilizes. The geo-accumulation (I_geo), the Hakanson index (E_rⁱ), and the risk assessment code (RAC) analyses of the hazard degree of Hg and As indicate that the risk of Hg pollution is high based on high Hg environment background value in Lake Caohai wetland, As is at a low level of pollution risk level and less affected to the environment. In this study, the distribution of Hg and As speciation and ecological risks on different water level gradients of Grus nigricollis habitat in Lake Caohai wetland were studied, and the effects of water-level gradient on heavy metal/semimetal distribution in sediment/soil were discussed. It provides a reference for the assessment of ecological effect of water level rise in the Lake Caohai wetland.