In order to study Fe3O4-Polypyrrole (Fe3O4-PPy) core–shell nanocomposite in the diagnosis oftumor markers in the diseased gastric tissues of early cancer patients, a total of 160 cases ofpatients, who were confirmed as early gastric cancer by gastroscopy or postoperative pathologyat a designated hospital of the study from December 2014 to December 2018, were selected asresearch objects and were divided into two groups of observation and control group with 80 casesin each group. For each patient in the two groups, two pieces of diseased gastric tissue werefirstly taken through gastroscopy; then the observation group applied Fe3O4-PPy with the particlediameter of 150–350 nm as carrier to detect the contents of carbohydrate antigen 19-9 (CA19-9),alpha-fetoprotein (AFP), carbohydrate antigen 242 (CA242), carcinoembryonic antigen (CEA) andcarbohydrate antigen 72-4 (CA72-4) in the diseased gastric tissue, while the control group directlydetected the contents of corresponding tumor markers; after the detections, the sensitivity, speci-ficity and diagnostic efficiency of each marker in the two groups of patients were calculated, andreceiver operating characteristics (ROC) curves with the areas under the curves (AUC) were drawnto analyze the correlation between the level of Fe3O4-PPy and the detection efficiency of gastriccancer markers. The results show that the detection sensitivity (82.17%, 80.32%, 79.48%, 84.63%,and 85.66%) and specificity (76.75%, 79.66%, 81.07%, 83.47%, and 85.24%) of CA19-9, AFP,CA242, CEA, and CA72-4 in the tumor tissue of patients in observation group for the diagnosis ofearly gastric cancer are higher than the sensitivity (78.66%, 79.25%, 76.18%, 82.11%, and 83.45%)and specificity (74.37%, 76.94%, 77.24%, 81.22%, and 81.59%) of that in control group with statistically significant differences (P < 005). Therefore, it is believed that the Fe3O4-PPy is of greatsignificance for the detection of early gastric tumor markers in the tissues of patients with earlygastric cancer, and has certain value for the auxiliary diagnosis of early gastric cancer and theobservation of therapeutic effects. This study results provide a reference for the further researchesof Fe3O4-PPy in the diagnosis of tumor markers in patients with early gastric cancer.Keywords: Fe3O4-PPy, Tumor Marker, Early Gastric Cancer, Core–Shell Nanocomposite