Abstract: The use of improved ER medium will enable cotyledons basis and cotyledon petiole of the Thea sinensis L. to develop embryoid. The cytohistological and morphological investigations on the changes in developing process of embryoid have been made in detail. Our works reveal that the embryoid of Thea sinensis L. are differentiated from the epidermal cell of cotyledons. The initial separating patterns of the embryogensis in embryo and embryoid are different. But it js more similar in their form-formative processes. We also found that the different kinds exogenous growth regulators and their quantity used for the cultural medium will affect the differentiations of embryoid and the formation of young plants.