The species composition of macrozoobenthos of Ulaagchny Khar Lake in Western Mongolia includes is a total of 43 species where chironomids are dominate. 7 species are listed in Mongolia for the first time. Productivity characteristics of macrozoobenthos are examined within the open water and ice periods in two representative biotopes (silted sands planted with high plants and clays) at the 3–5 m and 9–14 m depths respectively. The larvae and pupae of chironomids prevailed both in abundance and biomass troughout the lake, 27 species and larval forms are identified within that group. Amphipods as total subdominant and molluscs as 2nd subdominant at the 3–5 m depths are here.