Abstract：Objective Toinvestigate the caldiagnostic ofplasma RAS ciationdomain family1A(RASSFIA)gene methylation combined with tumor marker det）.Methods Atotal of 98 NSCLC patients admitted to Qinhuangdao First Fne 2023 toMa and 95 patients who underwent pulmonary examinatior he disease control group.Their general clinical data were arkers，and clinicopatho-logical features were analyzed. is of NSCLCwere analyzed by the multivariate Logistic regluated by the receiver operating characteristics(ROC)curve and 05 in smoking history，neuron specific enolase（NSE)，carci(CYFRA21-1)，and RASSFlA methylation levels between the NSC(P<0.05）inRASSFIA methylation levels,NSE,CEA,and CYFR21-1aracteristics such as tumor diameter,differentiation degree，and thatRASSFIAmethylationlevels (OR=1.071，95%CI：1.042-1.100)），NSE（OR=1.168，95%CI：1，CEA(0R=1.154，95%CI：1.121-1.187)，and CYFR21-1（OR=1.089，95%CI：1.023-1 nosis of NSCLC.Amodel predicting the occurrence of NSCLC was constructed using the principal component analysis (PCA)and partial least squares discriminant analysis (PLS-DA)，and the ROC curve analysis results showed that the area under the ROC curve（AUc"oc)，sensitivity，and specificity of the prediction model for the RASSFlA methylation level combined with NSE,CEA,and CYFR21-1were 0.922(95% CI; O.896-0.948)，O.897,and 0.851,respectively,which were higher than those of the RASSFlA methylation level, NSE,CEA,and CYFR21-1alone.ConclusionThe prediction model of plasma RASSFlA gene methylation level combined with tumor markers has high diagnostic value for NSCLC and can be used for the clinical diagnosis of NSCLC.