Abstract: Objective: To study the anti -tumor effect of CD3AK cell prepared from umbilical blood and to explore the recent curative effect on tumor cases and seek better immune index for biotherapy. Methods: IL-2 and IL-2+CD3Ab was used to induce LAK cell and CD3AK cell from umbilical blood mononuclear cells (UBMC). The expanding number and bio-activity of LAK cell and CD3AK cell were examined in different time after culture, the T cells subgroup absolute count and the NK activity of peripheral blood mononuclear cells (PBMC) of malignant tumor patients were examined before and after CD3AK cell adopting immune therapy as well. Results: The number and bio-activity (NK killing cancer K562) of LAK and CD3AK cells reached their peaks on 11th day. The number of LAK and CD3AK cells were 18 folds and 24 folds of the number before culture; the T cells subgroup absolute count of peripheral blood had grown up obviously: all T cell rise 66%, Th cell rise 68%, Ts cell rise 58%; the NK activity (killing K562 cell) of PBMC had grown up to 81% from 63% by CD3AK cell transfusing, the even rising ratio is 28%. Conclusions: 1) The UBMC is a potential and better source of predecessor for LAK and CD3AK. 2) The NK activity of LAK and CD3AK cells from UBMC reached their peaks at 11th day after culture, and the NK activity of CD3AK cell is much greater than that of LAK cell. 3) The T cells subgroup absolute count and the NK activity of malignant tumor patient's PBMC can be obviously elevated by transfusing CD3AK cell. 4) The test of the T cells subgroup absolute count and the NK activity of PBMC may become a recent objective immune index for tumor biotherapy.