Objective: We aimed to study the effect and mechanism of low-dose radiation (LDR) on adaptive response of gastric cancer cell. Methods: SGC7901 cells were cultured in vitro, and divided into 4 groups: control group (D0 group), low-dose radiation group (D1 group, 75 mGy), high-dose radiation group (D2 group, 2 Gy), low-dose plus high-dose radiation group (D1 + D2 group, 75 mGy + 2 Gy, the interval of low and high-dose radiation being 8 h). Cell inhibition rate was detected by cytometry and CCK8 method; the proportion of cell cycle at different times after irradiation was determined by using a flow cytometry. The ATM mRNA levels were detected by using quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). Results: There was no significant different between groups D0 and D1, groups D2 and D1 + D2 cell inhibition rate (P > 0.05). There was a significant increase G2/M arrest in groups D2 and D1 + D2 than groups D0 and D1 after 6 h of radiation and did not recover at 48 h (P < 0.05). The ATM mRNA expression of group D2 and D1 + D2 increased highly than that of group D0 and D1 (P < 0.05). However, differences between group D2 and D1 + D2, group D0 and D1 were not statistical significant (P > 0.05). Conclusion: LDR cannot induce adaptive response in SGC7901 cells in vitro, which may be associated the regulation of cell cycle, and its ATM mRNA expression cannot be affected by 75 mGy X-ray radiation. Objective: We aimed to study the effect and mechanism of low-dose radiation (LDR) on adaptive response of gastric cancer cells. Methods: SGC7901 cells were cultured in vitro, and divided into 4 groups: control group (D0 group) dose radiation group (D1 group, 75 mGy), high-dose radiation group (D2 group, 2 Gy), low-dose plus high-dose radiation group (D1 + D2 group, 75 mGy + 2 Gy, the interval of low and high-dose radiation being 8 h). Cell percentage was detected by cytometry and CCK8 method; the proportion of cell cycle at different times after irradiation was determined by using a flow cytometry. The ATM mRNA levels were detected by using quantitative real-time There was no significant difference between groups D0 and D1, groups D2 and D1 + D2 cell inhibition rate (P> 0.05). There was a significant increase in G2 / M arrest in groups D2 and D1 + D2 than groups D0 and D1 after 6 h of radiation and did not recover a (P <0.05). The ATM mRNA expression of group D2 and D1 + D2 increased highly than that of group D0 and D1 (P <0.05). However, differences between group D2 and D1 + D2, group D0 and D1 were not statistically significant (P> 0.05). Conclusion: LDR can not induce adaptive response in SGC7901 cells in vitro, which may be associated with the regulation of cell cycle, and its ATM mRNA expression can not be affected by 75 mGy X-ray radiation.