The members of the order Chlorocococales grow chiefly in the freshwater bodies, especially in quiet waters, such as lakas, pools, ponds and reservoirs etc.. The studies of this order are of importance to basic theoretical research of algal taxonomy, aquaculture and the applied subjects dealing with the eviromental science, such as purification of water and so on. Up to the present, the classification of the Chlorococcales is still in a state of great confusion. According to the evolutionary theory and looking back to the whole process of the biological evolution, the auther consided that the main characteristics used as the taxonomic basis of organisms, are not used only to identify different species, and more important in showing the phylogeneric process, mainly for the morphological structures. We would choose these characteristics as reasonable criterion to establish the phylogeny of this order. According to the types of plant-body construction of the Chlorococcales in a phylogeneric line from simple to complex forms, the auther divided them into four main groups: unicellular, colonial, protocoenobic and eucoenobic types. This opinion could be taken as the taxonomic basis in arranging the position of the variety of the families among the order, and a new systematics of the Chlorococcales has been put forward. The algal specimen have been collected from 30 cities and counties in Hubei Province and identified near 2000 bottles of them stored in liquid from the four fivths cities, regions and counties of the whole province. The result of identification showed that the plants of Chlorococcales in Hubei includes 13 families, 33 genera, 247 species and varities (with 3 forma), in which there are 12 new species and 2 new varieties and 27 genera, 61 species and varieties are new records in China.