Provided are a universal shaft assembly and a high-frequency impact screw drill applying the same. The universal shaft assembly comprises a universal shaft, the two ends of the universal shaft are sleeved with externally-sleeving joints to be connected with a rotor and a transmission shaft of the screw drill correspondingly. Each externally-sleeving joint comprises an externally-sleeving joint convex part and an externally-sleeving joint concave part. The externally-sleevingjoint convex part is inserted into the externally-sleeving joint concave part and is connected with the externally-sleeving joint concave part in a clearance mode. The other end face, not connected with the externally-sleeving joint concave part, of the externally-sleeving joint convex part is provided with a first connection head which is used for connecting the rotor or the transmission shaft. The other end face, not connected with the externally-sleeving joint convex part, of the externally-sleeving joint concave part is provided with a second connection piece used for connecting the universal shaft. A connection base is arranged in the center of the inner side of the externally-sleeving joint convex part, concave grooves are formed in the connection base in the radial direction, the two ends of the universal shaft are provided with convex teeth which correspond to the concave grooves, at least two connection holes are formed in the inner side of the externally-sleeving joint concave part, and the two connection holes are connected through a small connection shaft.