The risk of CRC in the XPD gene A allele carriers (GA/AA) was significantly higher in patients who smoked ≥16 packs/year (OR = 2.838, 95%CI = 1.490–5.433, P=0.001; adjusted OR = 1.570, 95%CI = 1.201–1.976, P=0.001); the risk of CRC in the hOGG1 gene G allele carriers (CG/GG) increased significantly (OR = 9.938, 95%CI = 5.061–19.694, P<0.001; adjusted OR = 3.031, 95%CI = 2.184–4.225, P<0.001); the risk of CRC in the XRCC4 gene T allele carriers (GT/TT) also increased significantly (OR = 19.695, 95%CI = 7.903–51.271, P<0.001; adjusted OR = 2.793, 95%CI = 2.235–3.222, P<0.001). The gene discussed is OGG1; the disease is colorectal carcinoma.