In this study, the Al-12Si alloys were prepared by the ultrasonic-assisted laser metal deposition method. The effect of laser power, scanning speed, scanning spacing and ultrasonic power on the density of the deposited layer was investigated. The microstructure and mechanical properties were analyzed using metallographic microscope, scanning electron microscope, electron backscatter diffraction technology and tensile test. The results show that the density of deposited samples increases with the enhance of laser power and ultrasonic power, and first improves and then reduces with the increase of scanning speed and scanning spacing. When the process parameters of laser power 1 100 W, scanning speed 6 mm/s, scanning spacing 1.0 mm, and ultrasonic power 1 000 W were used, and the same deposition layer was scanned twice perpendicular to each other, the sample with the highest density of 99.1% could be obtained. At this time, the deposited layer was mainly composed of α-Al solid solution with grain size of 2.5~75 μm and Al-Si eutectic. Due to the improvement of the density, the tensile strength and elongation of the ultrasonic optimal test specimen were 17% and 53% higher than those of the optimal test specimen without ultrasonic vibration.