Abstract: Objective To investigate the expression of monocarboxylate transporter proteins (MCTs) in gastric cancer tissues and its clinical significance.Methods A total of 56 patients who were admitted to Xuzhou Central Hospital from January 2018 to December 2020 and pathologically diagnosed with gastric cancer were selected. Their gastric cancer tissues and adjacent normal tissues, as well as positron emission tomography/computedtomography (PET/CT) results were collected. The GEPIA2 and kmplot databases were adopted to analyze the expression of MCT1-4 in gastric tissues and its relation with disease classification and prognosis. The expression of MCT4, glucose transporter 1 (GLUT1) and hypoxia inducible factor-1α (HIF-1α) was detected by immunohistochemistry. The relationship between MCT4 expression and GLUT1 and HIF-1α were analyzed by GEPIA1 database.Results According to GEPIA1 online analysis, the levels of MCT1 and MCT4 mRNA were significantly higher in gastric cancer tissues, compared with those in the non-gastric cancer tissues (P<0.05). No statistical difference was found MCT2 and MCT3 expression (P>0.05). There was no relationship between MCT1 and MCT4 gene and the classification of gastric cancer (P>0.05). According to kmplot database, gastric cancer patients with high MCT1 mRNA expression presented increased overall survival (OS)(P<0.001), while those with high MCT4 mRNA expression had decreased OS (P<0.001). Furthermore, MCT4 protein levels were significantly elevated in gastric cancer tissues compared with adjacent normal tissues (P=0.0006). GEPIA2 analysis and immunohistochemical results indicated that MCT4 expression was positively correlated with GLUT1 and HIF-1α protein.Conclusions MCT4 is involved in regulating the reprogramming of GC glucose metabolism and tumor microenvironment, which is closely related to the occurrence and development of GC and can be used as a potential prognostic marker.