The invention relates to a combined technological method for maximum production of light aromatic hydrocarbon from hydrogenated diesel oil. The method includes: firstly letting hydrogenated diesel oil enter an I section adsorption separation device to obtain an I section alkane component rich in cycloalkane and alkane and an I section heavy aromatic hydrocarbon component rich in aromatic hydrocarbon; sending the I section alkane component into a cycloalkane dehydrogenation reactor to obtain a cycloalkane dehydrogenation product rich in aromatic hydrocarbon, conducting gas-liquid separation, and letting the liquid phase enter an II section adsorption separation device so as to obtain an alkane component rich in alkane and an II section heavy aromatic hydrocarbon component rich in aromatic hydrocarbon; letting the I section heavy aromatic hydrocarbon component, the II section heavy aromatic hydrocarbon component and hydrogen enter a heavy aromatic hydrocarbon conversion reactor to obtain a light aromatic hydrocarbon product rich in BTX, and performing separation to obtain hydrogen, returning the hydrogen and part of C9<+> heavy aromatic hydrocarbon together to the heavy aromatic hydrocarbon conversion reactor for further reaction, and taking the rest C9<+> heavy aromatic hydrocarbon, dry gas, liquefied gas, C5-C6 non-aromatics and BTX product as the products. The method realizes maximum production of light aromatic hydrocarbon, and has the advantages of strong raw material adaptability, high yield of light aromatic hydrocarbon, low hydrogen consumption and no need for aromatic hydrocarbon extraction.