The invention provides a method for preparing a high-mobility AlGaN/GaN electronic power device on a Si substrate. A 20-30nm low-temperature AlN core-forming layer is grown on the Si substrate firstly by adopting a metal organic chemistryvapor phase epitaxy technology; then a high-temperature 200-300nm AlN buffer layer is grown; on the basis, a 300nm Al0.2Ga0.8N stress regulation and control layer is grown under a variable temperature condition; a 800-1,000nm high-resistance GaN epitaxial layer is grown; 10-20 periods of Al0.2Ga0.8N/GaN stress regulation and control layers are grown; the 800-1,000nm high-resistance GaN epitaxial layer is grown; and then a 15nm AlGaN/1nm GaN is grown. According to the method provided by the invention, the stress, warping, and defects existing in the hetero-epitaxy technology so far are effectively solved; and the crack-free high-mobility AlGaN/GaN electronic power device is obtained.