EL-4 lymphoma cells were irradiated with the inductive doses (D1: 25 ~ 200 mGy, dose rate: 12.5mGy/min) and the challenging dose (D2: 0.5 ~ 3.0 Gy, dose rate: 287 mGy/min), and the time interval between D1 and D2 was 6 h. The percentage of cell apoptosis and the expressive levels of cell apoptosis-associated gene proteins were measured with flow cytometry. The percentages of cell apoptosis in the D1 + D2 group with 25 ~ 100 mGy (D1) and 1.5 Gy (D2) or 75 mGy (D1) and 25 ~ 200 mGy (D2) were significantly lower than those in the D2 group. As compared with the D2 group, the positive percentage of cell Bcl-2 protein expression increased somewhat, and Bax decreased significantly, meanwhile the ratio of Bcl-2/Bax increased significantly and p53 decreased somewhat in D1 + D2 group with 25 ~ 100 mGy (D1) and 1.5 Gy (D2). The adaptive response of EL-4 lymphoma cell apoptosis could be induced by pre-irradiation with 25 ~ 100 mGy. Meantime, the expressive levels of cell apoptosis-associated gene Bcl-2, Bax and p53 proteins could change accordingly with cell apoptosis. These gene protein changes may play an important role in the mechanism of the adaptive response.