Abstract: Objective To explore the radioresistance difference between SHG-44 and U251 cell line,investigate the correlation among radioresistance, APEX1 mRNA expression and cell cycle distribution. Methods Colony formation assay was performed to determine the radioresistance difference, APEX1 mRNA expression was determined by RT-PCR,cell cycle distribution was investigated using flow cytometry, their correlation were analyzed by linear correlation. Results Compared with U251(pathological grade: WHO Ⅳ),SHG-44(pathological grade: WHO Ⅱ-Ⅲ) was higher radioresistant(SF2U251=0.58±0.02，SF2SHG-44=0.70±0.15，t=3.19，P＜0.05),but its APEX1 mRNA expression was lower(1.17±0.04 vs.0.70±0.18，t=19.92，P＜0.05),its G₁ phase proportion was increased(60.13±3.26 vs. 51.72±5.14，t=2.51，P＜0.05),S phase proportion was decreased(18.57±0.64vs. 28.80±2.96，t=5.09，P＜0.05),and there is no significant difference in G₂ phase between U251 and SHG-44(17.63±3.91 vs. 21.78±4.81，t=1.25，P＞0.05),G₁ phase arrest was correlated to radioresistance（r=0.735，P＜0.05）. Conclusion Pathological grade and radioresistance may be negatively correlated in glioma,there may be different radioresistance mechanisms in different types of gliomas, APEX1 is not correlated with radioresistance in glioma SHG-44,but G1 phase may be correlated with radioresistance in glioma SHG-44.