The invention discloses a 3D print head. The 3D print head is characterized by comprising an ultrasonic transducer, an ultrasonic amplitude transformer and an ultrasonic welding rod. The ultrasonic transducer is connected with the ultrasonic amplitude transformer, the ultrasonic welding rod is connected with the ultrasonic amplitude transformer, the ultrasonic welding rod is provided with a through hole which is used for conveying a printing material, the through hole extends to the end portion of the ultrasonic welding rod, and a fusing device which is used for heating the printing material into a molten state is also arranged. According to the 3D print head, the ultrasonic transducer and the ultrasonic amplitude transformer generate and amplify ultrasonic vibration, the bottom of the ultrasonic welding rod makes direct contact with the molten material, the ultrasonic vibration is transmitted into the molten material, when the metal printing material is printed in a vacuum or protective atmosphere, the molten metal makes contact with a printed workpiece, an upper metal layer is connected with a lower metal layer, under the ultrasonic vibration environment, structure grains are refined, pores, cracks, incomplete fusion and other defects are reduced, the structure performance is improved, the combination strength between the layers is improved, and the printing quality is further improved.