Here, we established a prognosis model for GC based on five m5C-related subtypes and four DEm5CRGs (APOD, ASCL2, MFAP2, and CREB3L3) as biomarkers, employing 405 GC samples about second-generation sequencing data, clinical information, and copy gene variation information from the TCGA database, and at last, verifying the four biomarkers in GC cells compared with the human immortalized normal gastric cells by the RT-qPCR method, which is usually missing in bioinformatic analysis. The gene discussed is CREB3L3; the disease is gastric cancer.