In this study, we were aimed to assess the diagnostic value of Alu-based serum CFD in GC patients by bDNA, explore the possible correlation between serum CFD and GC-associated tumor markers of CEA, CA19-9, CA72-4 and CA50, and evaluate the assistant diagnostic value of serum CFD with bDNA technology in early screening and monitoring progression. The gene discussed is CEACAM5; the disease is gastric cancer.