Of 65 species of Mysidacea previously reported from the South China Sea by the present author, 46 species were collected from the northern part. The present paper reports results of further study of the materials collected from the northern South China Sea in the area 17°00′-23°00'N, 108°00′-117°30′E covered by the 1958-60 National Comprehensive Oceanographic Survey. Of 12 new and rare species belonging to 2 families and 9 genera are reported, 10 are new to science, 2 are recorded for the first time from Chinese coast of the South China Sea. Two new genera Liuimysis and Shenimysis are established to accept the new species Liuimysis longicauda and Shenimysis cordata. The type specimens are deposited in the Institute of Oceanology, Chinese Academia of Sciences (Qingdao). The twelve species are listed below：