AbstractThe study of the host-prokaryotic symbiosis in sarcodines and flagellates is an improtant part 0f the exploration of the Origin and evolution of eukaryocytes．Until now ,bacteria endosymbionts have been found in more than 20 species 0f amoebae and 70 species of flagellates. Most of the symbiotic bacteria are sustained in symbiontophoric vacuole of the host's cytoplasm ,whereas the nuclear symbionts are observed in few flagellate species．The biogenesis 0f membranes of symbiontophoric vaeucles an important aspect 0f the amoebaebacteria system establishment，also，the symbiont may become essential cellular components 0f amoebae by supplementing a genetic defect for an amoebae’s house-keeping gene that is brought about by an action of the symbiont themselves．Studies on the endosymbiotic systems 0f Glaucophyceae-cyanellae have proved that the chloroplast originated from a single ancestral symbiotic cyanobacterium.Trypanosomatids quite often contain endosymbiotic diplosomes in their cytoplasm,also,it is deduced that the diplosome have been inherited by trypanosomatids from bodonids.It is supposed that:(1)further study on basic stages of origin of symbiotic relationship between flagellates and prokaryotes may formulate the major principles of the origin of symbiotic systems of protozoa,and still further,furnish the theoretical evidences of the endosymbiotic origin of eukaryocytes;(2)profound study on the amoebae-bacteria system will probably produce testimony to the theory of endosymbiotic origin of eukaryocytes at the aspect of the evolution of genetic fine structures and metabolic regulation at molecular level.