The invention discloses a method for obtaining stem cell by using serum of the same cord blood, belonging to the field of biotechnology and tissue engineering. Serum of the same cord blood is used to replace fetal calf serum, no cell factor or stroma cell support is added, and the strategy of combining a microcarrier and a bioreactor is adopted, thus realizing co-culture of cord blood source hemopoietic stem cell and mesenchymal stem cell. The method of the invention can support fine augmentation of UCB-HSCs and UCB-MSCs under three-dimensional conditions, completely replace the role of fetal calf serum and avoid immunological rejection among variants; cytodex-s microcarrier can provide adhesion surface for UCB-MSCs with adherence growth characteristics, so that the UCB-MSCs can realize possible adherence suspension culture in a three-dimensional dynamic environment; the natural settling method is adopted to separate and obtain the suspending UCB-HSCs and the UCB-MSCs which adheres to the microcarrier.