Abstract: The present disclosure discloses a quantum dot (QD). The QD has a core-shell structure, and specifically has a structure of CdZnSeS/CdZnSe/CdZnS/ZnS, where there is a metal halide ligand between a CdZnS shell and a ZnS shell and outside the ZnS shell. The present disclosure also discloses a preparation method of the QD and a QD composite material prepared from the QD. The QD disclosed by the present disclosure has a small full width at half maxima (FWHM), excellent optical performance, and high stability. In the preparation method of the QD, an intermediate shell layer is prepared through alternate growth of anions and cations, and in addition to the introduction of a metal halide precursor, a long-chain alkanol is added to a shell to further improve the stability.