<p>Permeability is crucial for coalbed methane extraction efficiency. Both hydraulic fracturing and ultrasonic treatment can enhance coal seam permeability, with ultrasonic-assisted hydraulic fracturing showing significant potential. Experiments measured the permeability of coal samples before and after treatment under various stress conditions. The results showed that effective stress significantly impacts permeability, but the underlying cause of stress variation is equally important. Changes in axial pressure result in smaller variations in effective stress and have limited effects on permeability, leading to gradual decrease. Confining pressure has a greater influence, causing an exponential decline in permeability as effective stress increases. Ultrasonic-assisted hydraulic fracturing enhances permeability more effectively than either method alone. When used individually, these methods increased permeability (from initial value of about 1 × 10^-13 cm²) by about 90%, while their combined use resulted in nearly a tenfold increase. At an effective stress of 1.38 MPa, the rate of change in permeability due to ultrasonic-assisted hydraulic fracturing was more than 14 times greater than when using a single method. The stress sensitivity coefficient reflects the responsiveness of permeability to stress changes. Axial loading led to lower coefficients (0.0–0.3) while confining pressure resulted in higher coefficients (0.5–2.5), associated with significant reductions in permeability. This study provides valuable insights into ultrasonic-assisted hydraulic fracturing for coalbed methane exploitation.</p>