More than 300 years ago, A.van leeuwenhoek first saw many free-living and parasitic protozoa with a lens magnified about 270 times. He described the euglena as "green in the middle and white at both ends", and later generations honored him as the father of protozoology.

In 1758, C.von Linnaeus was named macrophyllum sp. and macrophyllum sp. By binomial method. G.A. Gore Defosses used the term protozoa in the first year of 18 17, but he also included coelenterates. Sebald (1845) gives the correct definition of protozoa. Ehrenberg described the observed protozoa in 1838, and put forward a preliminary classification system. At the beginning of the 20th century, the research on the classical classification of protozoa gradually expanded to the fields of physiology, nutrition, ecology and heredity. Since 1950s, due to the application of electron microscope, the research on protozoa has entered the submicroscopic level. In recent ten years, protozoa have been studied microscopically at the molecular level by using new technologies such as micro spectrophotometer and enzyme chemistry. At the same time, through the application of computer model, the ecology of protozoa was also studied at the community level.