The present invention provides a QD material, a preparation method, and a semiconductor device. The QD material includes at least one QD structural unit arranged sequentially along a radial direction of the QD material. Each QD structural unit has a gradient alloy composition structure with a changing energy level width along the radial direction or a homogeneous alloy composition structure with a constant energy level width along the radial direction. The disclosed QD material not only achieves higher light-emission efficiency of QD material, but also meets the comprehensive requirements of semiconductor devices and the corresponding display technologies on QD materials. Therefore, the disclosed QD material is a desired QD light-emitting material suitable for semiconductor devices and display technologies.