Use of a compound of general formula (A) which is a CFS-1R kinase inhibitor or a pharmaceutically acceptable salt thereof in the preparation of medicaments for treating diseases related to CSF-1R kinase signal transduction pathway or medicaments for regulating immunization. In vivo and in vitro studies show that the compound can significantly inhibit CSF-1R kinase activity; significantly inhibits the proliferation of a CSF-1/CSF-1R-driven mouse myeloid leukemia cell line, inhibits the survival of macrophages induced by CSF-1 and reverses M2 polarization phenotype of macrophages, and has an effect superior to that of the marketed medicament Pexidartinib. In a TAM enriched tumor model (MC38 model), the compound significantly antagonizes the tumor immunosuppressive microenvironment and exhibits significant anti-tumor efficacy. The compound has inhibitory effects on tumors that are not sensitive to immune checkpoint drugs, and can enhance the efficacy of immune checkpoint drugs, and has good clinical application prospects.