were selected as research objects and were divided into two groups ofobservation and control group with 80 cases in each group.For each patient in the two groups, two pieces of diseased gastric tissue were firstly taken through gastroscopy;then the observation group applied Fe3O4 with the particlediameter of 150–350 nm as carrier to detect the contentsof carbohydrate antigen 19-9 (CA19-9), alpha-fetoprotein(AFP), carbohydrate antigen 242 (CA242), carcinoembryonic antigen (CEA) and carbohydrate antigen 72-4(CA72-4) in the diseased gastric tissue, while the control group directly detected the contents of correspondingtumor markers; after the detections, the sensitivity, speci-ficity and diagnostic efficiency of each marker in the twogroups of patients were calculated, and receiver operatingcharacteristics (ROC) curves with areas under the curves(AUC) were drawn to analyze the correlation between thelevel of Fe3O4-PPy and the detection efficiency of gastric cancer marker. The detailed chapter arrangement is asfollows: Section 2 introduces the research materials andmethods; Section 3 analyzes the results; Section 4 analyzesthe diagnosis of tumor markers in gastric cancer tissues;Section 5 discusses; Section 6 is the conclusion.