The invention discloses a preparing method for 5,11-dihydro-6H-dibenzo[b,e]azepine-6 ketone. The preparing method includes the steps that raw materials of 5H-dibenzo[b,e]azepine-6 and 11-diketone are added into a reaction container, then a reaction solvent, zinc powder, organic acid and a catalyst are sequentially added, the temperature is started to be increased, and a stirring reaction is started when the temperature is the reaction temperature; the reaction is completed, the obtained reaction liquid is subjected to pressure reduction suction filtration, filtered liquid is extracted with trichloromethane, washing and drying are sequentially carried out after extraction, a trichloromethane solvent is subjected to pressure reduction recycling, and the 5,11-dihydro-6H-dibenzo[b,e]azepine-6 ketone is obtained. Compared with the prior art, the per-kilogram cost of the 5,11-dihydro-6H-dibenzo[b,e]azepine-6 ketone prepared with the method is reduced by 800 yuan to 1,000 yuan, the total yield is increased by 3% to 5%, industrial production can be directly achieved, and the remarkable economic benefits are achieved.