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Ultrasound is a physical food processing technology with promising industrial application prospects. To develop an ultrasound device suitable for food processing, the COMSOL multiphysics simulation software was used to numerically simulate and calculate the sound field distribution of a slit-type continuous ultrasound device under single-frequency (28kHz and 40kHz) and dual-frequency (28/40kHz) modes. The accuracy of the simulation model calculation was verified through an aluminum foil corrosion test. The simulation results showed that the single-frequency ultrasound sound field generated a negative-phase sound pressure directly below the transducer, and a positive-phase sound pressure with stable vibration was formed in the radiation intersection area around the transducer. The results of the aluminum foil corrosion test confirmed that the surface of the aluminum foil showed an irregular wavy deformation in the negative-phase sound pressure area and a granular pitting corrosion in the positive-phase sound pressure area. By calculating the relative standard deviation of the absolute total sound pressure of the ultrasound sound field directly below the transducer and in the radiation area around the transducer from the simulation data, it was obtained that the lowest relative standard deviation of 28kHz was 0.764, the lowest relative standard deviation of 40kHz was 0.960, and the lowest relative standard deviation of 28/40kHz was 0.658. The lowest relative standard deviation of the 28/40kHz dual-frequency ultrasound was 86.1% of that of the 28kHz single-frequency ultrasound sound field and 68.5% of that of the 40kHz single-frequency ultrasound sound field. The research result showed that the distribution of the dual-frequency ultrasound sound field was more uniform, which can provide a basis for the research and development of efficient food ultrasound processing equipment and offer guidance for the application of slit continuous ultrasound in food processing.