Abstract: The disclosure provides a method for removing a cancer tumor stem cell and then further removing a tumor cell and provides an application of a drug molecule and its preparation in tumor treatment or prevention. On the one hand, by inducing the death of immunogenic cells, the anti-tumor immune response is enhanced. On the other hand, indoleamine-2,3-oxygenase is inhibited, immune cells, cytokines, amino acids, etc. are regulated, which improves the niche of cancer stem cells and makes them no longer conducive to the growth of cancer stem cells. Stem cell dormancy is lifted, and the sensitivity of cancer stem cells to chemotherapy drugs and immune cells is enhanced, so that cancer stem cells and tumor cells are effectively killed, and the efficacy of tumor treatment is improved.