The invention provides 7-(4-chlorphenyl)-5,6-dihydro-7aH-benzo[h]1,2,4-triazolo[3,4-b]quinazoline-5,6-diketone and a synthetic method thereof. The method comprises the following steps of: uniformly mixing 3-amino-1,2,4-triazole, p-chlorobenzaldehyde, 2-hydroxyl-1,4-naphthaquinone and p-methylbenzene sulfonic acid with a usage amount of catalyst, heating and stirring, controlling the temperature at 110-125 DEG C and reacting for 2.5-3 hours. The 7-(4-chlorphenyl)5,6-dihydro-7aH-benzo[h]1,2,4-triazolo[3,4-b]quinazoline-5,6-diketone prepared according to the invention introduces chlorine atoms, thus having stronger activity and being more beneficial to absorption. The method provided by the invention is green and environment-friendly, and has the characteristics that the raw materials are available, the operation is simple and the yield is high.