Provided in the invention is a satellite-borne ray-energy nanobattery comprising silicon nanowires, a cesium iodide layer, a bulk silicon emitter, an exhaustion region, a bulk silicon base and a back panel. The silicon nanowires absorb light from an ultraviolet band, a visible band and an infrared band to generate free electrons; and the photon energy is collected by the silicon nanowires, thereby increasing the power density. The cesium iodide layer absorbs a high-energy X ray and a high-energy gamma ray and converts the high-energy ray photon into a photo at the visible band. The bulk silicon emitter and the bulk silicon base collect excessive carriers and absorb perpendicular incidence and secondary reflection photons. A built-in voltage is kept in the exhaustion region to guarantee separation of a photon-generated carrier. The back panel reflects the photons and the photo absorbing probability by the bulk silicon is increased. According to the invention, the surface coating structure of the solar cell is made of a cesium-iodide scintillation crystal material and the response band of eh current solar battery is broadened to the ray region including the x ray and the gamma ray, so that a certain radiation damage protection effect is realized. And thus the power supply demand of the spacecraft in a high-radiation low-illumination space environment can be satisfied.