The invention discloses an application of a compound as a JAK-STAT3 signal passage inhibitor, and particularly relates to an application of a compound with a formula I or pharmaceutically acceptable salt of the compound in the process of preparing an anti-tumor medicament. The application provides a novel treating candidate medicament for a tumor patient, thereby probably further improving the treatment effect on the patient and improving the prognosis of the patient. The compound with the formula I or the pharmaceutically acceptable salt of the compound has the effect on various tumor cells, which indicates that the compound can be used for treating various cancers including cerebral tumor, genitourinary system tumor, lymphatic system tumor, stomach cancer, laryngeal cancer, nasopharyngeal cancer, skin cancer, bone cancer, blood cancer, leukemia, breast cancer and histiocytic lymphoma, non-small cell lung cancer, small-cell lung cancer, lung adenocarcinoma, lung squamous cell cancer, pancreatic cancer, prostatic cancer, liver cancer, epithelial cell cancer and the like. The definition of genes in the formula refers to description for details.