The invention discloses a method for preparing canned diced tomatoes. The method specifically relates to raw material inspection, pre-washing drifting separation, a scraper type high-altitude lifting machine, an overhead storage tank, raw material selection, tomato washing and sorting in a bubbling tank, scald peeling, dicing and sorting, tin can inspection, a breaking system, preheating and softening enzyme deactivation, refining and pulping, vacuum concentration, pre-sterilization, juice and dice canning, a heating power exhaust system, filling and sealing, heat sterilization with boiled water, packaging, standing and checking, and storage and transportation. During scald peeling, peels are cured through high-temperature steam and then delivered to a vacuum section for condensation so as to shrink, crack and fall off, and tomatoes subjected to steam scald peeling are rubbed and rotated through rollers so that peels can completely fall off. According to the method, during peeling, after high-temperature steam scalding, tomatoes are rubbed and peeled through the rubber rollers, so that the effects of quick peeling, tomato integrity, and lycopene loss reduction are realized, fully-automatic mechanical continuous production is achieved, labor intensity is relieved, product competitiveness is improved, and market share is increased.