The invention discloses a black silicon preparation technology combining ion beam surface activation sputtering and reactive-ion etching. The problems that an existing black silicon preparation technology is complex and low in etching accuracy are solved. The black silicon preparation technology comprises the steps that first, a silicon wafer is placed in a vacuum chamber; second, a low-energy ion beam is used for evenly irradiating the silicon wafer, and periodical nanostructures are evenly formed on the surface of the silicon wafer; third, the silicon wafer irradiated in the second step is placed in the vacuum chamber for reactive-ion etching to generate black silicon. According to the black silicon preparation technology combining ion beam surface activation sputtering and reactive-ion etching, in the whole black silicon preparation process, the parameters involving the form of the silicon-surface nanostructures and the thickness of a black silicon layer and influencing the light reflection characteristic of the black silicon are controlled separately, the nanostructures on the surface of the black silicon and the thickness of the black silicon layer can be designed in advance, and the purpose of optimizing a black silicon structure so that any different requirements can be met is achieved; the silicon-surface nanostructures and the thickness of the black silicon layer can be controlled manually and flexibly, consumption of the black silicon layer is small, etching accuracy is high, the technological process is simple, and great practical value is achieved.