A new copepod species Metadiaptomus aliensis sp. nov., collected from lakes in the Qinghai-Tibetan Plateau, is described. M. aliensis sp. nov. is differentiated by total length of both sexes, the fifth leg of both sexes, and the right antennule of the male, compared with the similar species M. asiaticus Ul'yanin, 1875 and M. chevreuxi Guerne & Richard, 1894. The low temperature species M. aliensis sp. nov. survives in a wide salinity range from fresh to polyhaline water, and a wide alkalinity range from 6.12 to 40.39 mmol/L. The first generic record of M. aliensis sp. nov. in the Qinghai-Tibetan Plateau contributes to our understanding of the global biogeography of the subfamily Paradiaptominae.