Gansu is a province in the northwest of China that is well known for its rich grassland types and important alfalfa planting base in China. Among the key limiting factors in alfalfa products and high quality are insect and mite pests, particularly those occurring on root and stem parts. Mite populations were collected on alfalfa roots from Jiuquan City located in the northwest part of Gansu Province. This study aimed to identify the principle mite species infesting alfalfa in Gansu Province, by molecular and morphological characterization. DNA from 20 specimens and morphological data from 45 specimens (15 adult females, 20 adult males [10 homeomorphic and 10 heteromorphic] and 10 deutonymphs were used to confirm the identity of the mite species. The species present is described here as a new species (Sancassania alfalfa Shang & Li, sp. nov.).