The invention discloses an ultrasonic vibration assisted pipe fitting hydraulic forming device which comprises a first flat plate and a second flat plate vertically in parallel in a spaced mode. A transmission base is arranged between the first flat plate and the second flat plate. A group of supporting columns are arranged between the first flat plate and the second flat plate. A first guide column is arranged on the first flat plate. A first positioning ring is arranged at the bottom of the first guide column. A first sealed column is arranged at the hollow position of the first positioningring. The upward face of the second flat plate is sequentially provided with a liquid injecting base and a second positioning ring from bottom to top. A second sealed column is arranged at the hollowposition of the second positioning ring. A group of transverse plates are arranged on the transmission base. The inward ends of the transverse plates are provided with vertical plates. The transverseplates are connected with a transmission rod of the transmission base. The ultrasonic vibration assisted pipe fitting hydraulic forming device is simple in structure, convenient to detach and assemble, easy to operate, low in required die assembling force and forming force, high in pipe blank forming efficiency and high in forming section regularity, filling property, fittability and wall thickness uniformity and can form different positions of a pipe blank.