The dynamic spreading experiment of active solder on the surface of the porous graphite had been completed by the ultrasonic-assisted spreading technology. In this paper, the spreading process of an active solder droplet was captured by a high-speed camera. And the external characteristics of spreading under the action of the ultrasonic were analyzed. The spreading behavior and mechanism of active solder droplets on the surface of the graphite were studied under the action of ultrasonic wave .The results showed that ultrasonic amplitude was been decayed quickly in the surface of graphite, which makes it impossible for acoustic spreading on the surface of graphite. However, as these holes on the surface of the graphite were filled with solder, amplitude attenuation was decreased, acoustic spreading function was strengthen gradually. In the case of ultrasonic power is large enough, the liquid solder can spread on the graphite surface. Solder surface oxidation film is the key factors that hinder the solder spreading. The surface oxidation film of solder can be removed by ultrasonic vibration.