The invention discloses a three-dimensional double-sided silicon micro-strip detector and a preparation method thereof. The three-dimensional double-sided silicon micro-strip detector comprises an upper portion detection unit, a lower portion detection unit and a middle semiconductor base body, a plurality of mutually parallel upper semiconductor base bodies are uniformly inlaid in an upper troughelectrode of the upper portion detection unit, and upper central electrodes are inlaid in the upper semiconductor base bodies; a plurality of mutually parallel lower silicon base bodies are uniformlyinlaid into the lower trough electrode of the lower portion detection unit, and lower central electrodes are inlaid in the lower silicon base bodies; the heights of the upper semiconductor base bodies, the upper trough electrodes, the upper central electrodes, the lower silicon base bodies, the lower trough electrodes and the lower central electrodes are the same; the lower portion detection unitis located below the upper portion detection unit, and the lower portion detection unit and the upper portion detection unit are staggered for a certain angle in a horizontal direction. A silicon dioxide layer is generated at the surface of a silicon wafer by employing the gettering oxidation technology, the detector pattern is transferred onto the silicon dioxide layer through marking and photoetching, the etching and chemical deposition diffusion of the cathode electrode and the anode electrode are performed, and finally, damaging repairing and package are performed.