Abstract: In order to investigate the mechanism of the influence of dual-frequency ultrasonic fracturing technology on the damage characteristics of coal samples, a dual-frequency ultrasonic fracturing system was adopted, and different dual-frequency ultrasonic frequency treatments were applied to the coal samples. Through wave velocity detection, uniaxial compression-acoustic emission comprehensive experiment, and fractal dimension basic theory, we analyzed the fracture extension, damage and mechanical property changes of coal samples under dual-frequency ultrasound frequency, and investigated the synergistic effect of frequency superposition on the fracture extension as well as mechanical properties. The results show that high-frequency dual-frequency ultrasound significantly enhances the fracture complexity and connectivity; With the gradual increase of the second frequency from 20 kHz to 50 kHz, the length of the fissure was enhanced from 78.3 mm to 128.5 mm, which increased by 64.11%, and its growth rate increased exponentially with the second frequency from 15.49% to 89.53% rapidly, which was an increase of 477.99%; while the rate of change of the P-wave velocity continued to decrease with an approximate linear trend, slipping from −5.21% to −25.19%, a decrease of 383.49%, proving the key role of dual-frequency ultrasound and transient stress field in promoting microcrack sprouting, expansion and fissure network construction; the fractal dimension increment is enhanced from 0.0167 to 0.1255; the fractal dimension damage parameter also shows a linear increase from 0.0148 to 0.111, an enhancement of 6.5-fold; and the acoustic emission monitoring shows that the damage process is divided into three stages initial response, transitional expansion and critical acceleration; the cumulative ringing counts increased from about 3.4×10⁵ to about 4.8×10⁵, an improvement of 41.18%. The growth rates of the mechanical property parameters all showed a good linear decrease, and the damage process tended to be brittle. The growth rate of compressive strength decreased from −39.98% to −74.92%, a decrease of 87.39%; the growth rate of peak strain decreased from −17.68% to −48.99%, a decrease of 177.09%; the growth rate of brittleness index decreased from −50.59% to −87.20%, a decrease of 72.37%; and the growth rate of absorbed energy decreased from −61.27% to −93.62%, a decreased by 52.80%. Dual-frequency ultrasound promotes the formation of fissure network and reduces the mechanical properties of coal samples by enhancing the cavitation effect and stress concentration.