A spin transistor and a manufacturing method thereof are provided. The method includes defining a required area on a substrate by lithography; forming a doping area by ion-implantation, and forming a magnetoresistive film on the substrate. Finally, the method produces a spin transistor with the emitter, the base, and the collector in the same plane surface. The manufacturing method integrates the emitter, the base, and the collector into one plane, so that miniaturization of the spin transistor is achieved, and it is advantageous for the integration and subsequent packaging of the spin transistor and integrated circuit elements.