For further analysis of diagnostic value of serum cell-free DNA for glioma, we constructed the ROC curves, the AUC of Alu, MGMT, P16 was 0.904, 0.962, 0.599, respectively and identified that the methylation levels of Alu and MGMT in the serum had better diagnostic value than P16. Furthermore, combined analysis of Alu and MGMT revealed higher sensitivity for glioma diagnosis. The gene discussed is MGMT; the disease is glioma.