Abstract: The morphology of four widely distributed ciliates (Stylonychia mytilus, Tetmemena pustulata, Paramecium caudatum, Coleps hirtus) from Songhua River were studied using living observation and silver staining methods to complementally descript the living and ciliary pattern characters of Harbin populations of these four species including the arrangement of six rows of dorsal kineties after protargol impregnation and the specific statistics of the numbers of left and right marginal rows of S. mytilus. The results showed that the morphological features of Harbin population S. mytilus were basically consistent with previous reports, except that small membranes of Harbin population were more than previous populations. Compared with the Mohe population, the Harbin population T. pustulata were similar in morphology, infraciliature and the occurrence pattern, and had slightly higher in the number of left and right marginal and more micronuleus. Compared with the Qingdao populations of P. caudatum, Harbin population had significantly less collecting canals. Compared with previous populations, Harbin population of C. hirtus had slightly larger body size.