Disclosed are a liquid hydrogenated nitrile-butadiene rubber, a preparation method therefor and the use thereof. In the liquid hydrogenated nitrile-butadiene rubber: the content of acrylonitrile is 15-50%; the hydrogenation saturation is 75-99.5%; the weight-average molecular weight (Mw) is 3,000-60,000; the molecular weight polydispersity index (PDI) is 2.0-8.0; and the glass transition temperature (Tg) is lower than −28° C. The liquid hydrogenated nitrile-butadiene rubber is low in molecular weight and wide in molecular weight polydispersity, simultaneously has an excellent fluidity during processing and excellent mechanical properties after curing and has a unique application value in the field of special rubbers; and the preparation method therefor is simple and feasible in terms of the process.