To investigate the mechanism of ultrasonic compound laser etching,this paper used COMSOL software to simulate ultrasonic vibration-assisted laser ablation of metallic aluminum surfaces.The effect of ultrasonic vibration on the laser alteration mechanism and process was studied in comparison.It was found that the beginning of the laser ablation phase material was removed mainly by high temperature vaporization.As the ablation time increased,the mode of etching changed mainly to melt splash etching, which played a major role in the formation of ablation craters.The speed of laser etching of the material at different frequencies was also investigated.It was found that the introduction of ultrasonic vibration reduced the etching rate by 26.2%－39.43%.