Abstract: The family Lernaeidae forms into a monophyletic group of the order Cyclopoida by the following synapomorphies:The lst antenna short,lst maxilla uniramous or disappeared.The family Lernaeidae consists of 12 genera.Among them the genus Areotrancheilus was created by Wilson according to a single discovery.Henceforth no further descriptions have been made and most structures shch as antenna,oral appendage,thorax-pods and egg sac have been left unknown.Therefore it is diffcult to be compared with other genera and is not included in the present consideration of phylogenetic reconstruction.The family Cyclopidae is considered here as the outgroup of Lernaeidae.Polarities of characters recognized from all genera of Lernaeidae are determined by comparing to the outgroup Cyclopidae in order to distinguish apomorphic states from plesiomorphic states.Through comparative analysis,21 characters have been recognized and the states of these characters have shown mosaic distributions among 11 genera of Lernaeidae.Based on the mosaic distributions and of character states and the parsimonious principle,the intergeneric phylogenetic cladogram of Lernaeidae has been reconstructed.Clade Ⅰ and Ⅱ comprise the first sister group by 3 characters which show mosaic distributions.Clade Ⅰ consists of 5 genera and clade Ⅱ of 6 genera.Among 12 genera of Lernaeidae,7 genera occur in Africa,7 genera in Asia,3 genera in America,2 genera in Europe.The individuals of Lernaeidae are parasitized mainly on the fishes of Osteichthyes,particularly on fishes of Cypriniformes.Tropical Asia and Africa are the diversifying and originating centre of Cypriniformes.The distribution centre of Lernaeidae is situated also in tropical Asia and Africa,and is well agreed to the distribution centre of their hosts.This agreement demonstrates from one aspect the coevolution between parasites and their hosts.The water currents in Qinghai-Tibet plateau usually flow swiftly with a frigid water temperature.So far no individuals of Lernaeidae have been reported to parasitize on the fishes of the plateau.It is supposed here that the frigid water temperature be the main barrier to restrict the dispersion of Lernaeidae parasites.