The present invention belongs to the field of diagnosis and treatment of tumors, and relates to a HIF-2α small-molecule inhibitor and use thereof in treatment of tumors such as breast cancer and ovarian cancer. The small-molecule inhibitor is a compound represented by formula (I) or a stereoisomer, pharmaceutically acceptable salt, solvate or prodrug of the compound represented by formula (I). The small-molecule inhibitor mainly inhibits the proliferation of tumor cells by inhibiting HIF-2α protein, and can also inhibit the growth of CSCs with high expression of HIF-2α. The small-molecule inhibitor can be used as a novel anti-tumor drug to completely eliminate tumors and stem cells, and has broad application prospects.