An ultrasonic airflow severing resistance reducing device for vehicles, including an airflow severing blade assembly, shock-absorbing installation assemblies, ultrasonic vibration components, and a rubber sealing ring assembly; a bottom portion of the airflow severing assembly is provided with an accommodating cavity; a top end of each shock-absorbing installation assembly is fixedly connected to an inner cavity wall of the accommodating cavity; a bottom end of each shock-absorbing installation assembly is formed with a fixed installation bottom portion; the ultrasonic vibration components are installed on the inner cavity wall; the rubber sealing ring assembly is arranged and installed on the airflow severing blade assembly. The ultrasonic vibration components drive the airflow severing blade assembly to generate high frequency ultrasonic vibration to sever airflow.