Abstract: The author suggests to found a new scientific branch----evolutionary cell biology,which is an overlapping aprt of evolutionary biology and cell biology.The main subject of this new scientific branch is to study the origin and evolution of eukaryotic cells and their various living activities in order to examine them from the standpoint of how they arose in history and what principle stages they passed through in their development,and from the standpoint of their developments,to examine what they have become today.The content of evolutionary cell biology can be temporarily definded as the following:1.the prokaryotic ancestor of eukarvotes;2.the origin and evolution of eukaryotic cells and their organelles;3.the origin and evolution of various activities of eukaryotic cells and their organelles;4.the origin and evolution of the social relationships among cells;5.the motive force in the origin and evolution of eukaryotic cells;6.the "un-evolution" phenomena of organelles;7.the law and conditions on transformmg endocytosymbionts into cellular organelles;8.the origin and evolution of the special organelles in certain eukaryotes (e.g.the macronucleus in ciliates,the kinetoplast in kinetoplastid flagellates).For studying the problems of evolutionary cell biology,both synthetical analyses of evlutionary biology and experimental researches of cell biology are necessary and ought to be integrated with each other.The main cause of the "un-evolution" phenomena of cellular organelles and the author regarded that these phenomena were mainly induced by the transference of the focal point of evolution.