The invention relates to a process for preparing chrome acid anhydride from ferrochrome through an acid soluble electrolytic method. Ferrochrome is ground into fine powder and placed into a reaction still, acid is added to dissolve the ferrochrome, special substances are added for reaction with heating, trivalent chromium and ferrous ions are separated, then a trivalent chromium solution is placed into an electrolytic cell, the trivalent chromium is completely converted into hexavalent chromium through electrolytic oxidation, and chrome acid anhydride products are prepared. Through the process, series chromium compounds including dichromate, chromium sulfate, chromic chloride, chromic oxide, chromic hydroxide, a chrome tanning agent, chromium picolinate and chromium nicotinate, iron series pigment including ferrous oxalate, iron blue and ferbam, new materials including silicon and carbon, and new energy, namely hydrogen, are prepared simultaneously. The process is advanced, short in technological process, capable of saving energy and environmentally friendly, the produced products are good in quality, high in value and good in benefit, and the sustainable development of the chrome salt industry can be better prompted.