Four new species of Hydrocassis DEYROLLE & FAIRMAIRE and one new species of Ametor SEMENOV (Coleoptera: Hydrophilidae) are described: H. anhuiensis [Anhui, Jianxi], H. pseudoscapha [Anhui], H. sichuana [Sichuan], H. uncinata [Laos, Yünnan], and A. elongatus [Sichuan]. Faunistic notes on Hydrocassis lacustris (SHARP), H. imperialis (KNISCH), H. scapha d'ORCHYMONT, H. scapulata DEYROLLE & FAIRMAIRE, H. taiwana SATÔ, Ametor rudesculptus SEMENOV and A. rugosus (KNISCH) are given. Hydrocassis imperialis is recorded from Anhui for the first time, H. scapha from Anhui, Fujian, Guizhou, Jiangxi and Sichuan, H. scapulata from Gansu and Ametor rudesculptus from Himachal Pradesh (India). The first record of the genus Hydrocassis for Nei Mongol is presented.