Laser additive remanufacturing technology based on laser cladding has shown significant advantages and great potential in the repair and remanufacturing of damaged parts. However, the rapid heating and cooling process during laser cladding leads to the formation of micro-cracks, pores, residual tensile stress, etc. in the cladding layer. In order to improve the quality of laser cladding, ultrasonic assisted laser cladding has become one of the hot spots in current research. In this study, the wetting behaviors of the molten pool with and without ultrasonic vibration were compared to investigate the influence and mechanism of ultrasonic vibration on the wetting behavior, providing reference for high-quality ultrasonic assisted laser cladding.Inconel 718 substrates were polished and cleaned by alcohol to remove surface impurities. A laser beam with power of 1 kW and a spot diameter of 2 mm was used. Ultrasonic vibration with a frequency of 20 kHz and amplitude of 50 μm was transmitted from the bottom of the specimen to the molten pool. A forward wire feeding with a feeding angle of 45° was applied. The scanning speed and the wire feeding speed were 8 mm/s and 9.3 mm/s, respectively. During the experiments, the transition behaviors of the molten pool were captured by a high-speed camera, and the profiles of the molten pool were extracted by Canny algorithm. After the experiments, the macro morphology of the specimens was observed using a stereo microscope (Nikon, SMZ745T) and a confocal microscope (Keyence, VK-X1000). An optical microscope (Zeiss, Axio Imager2) was used to observe and analyze the microstructure of the cladding zone.Significant fluctuation occurred on the surface of metal droplet with ultrasonic vibration. And the contact area between the metal droplet and the substrate increased by 39.3% with the effect of ultrasonic vibration, indicating the increase of wettability. The area of the molten pool in the laser cladding increased significantly caused by ultrasonic vibration. When a stable liquid-bridge transition was reached in the laser cladding, the area of the molten pool with ultrasonic vibration was 2.8 times of that without ultrasonic vibration. With the increase of ultrasonic power, the height and depth of the cladding layer decreased while the width increased. The dilution rate of the cladding layer was also reduced by ultrasonic vibration. And the cladding layer gradually varied from an arc profile to be relatively flat. When the ultrasonic power ratio was 80%, the height of the cladding layer was 75.2% of that without ultrasound, suggesting significant improvement of the wettability between the cladding and the substrate. In addition, the growth direction of the grains changed and the epitaxial growth of dendrites was inhibited. In addition, the turning dendritic structure at the top of the cladding layer became narrow with ultrasonic vibration. The mechanisms of ultrasonic vibration on the molten pool were discussed based on the experimental results. In the laser cladding process, ultrasonic vibration is able to promote the wetting of melt and accelerate the melt flow of the molten pool, which leads to a relatively flat cladding layer. The area of molten pool increased, resulting in the variation of the grain growth direction and the length of dendrites.