A transmission shaft assembly includes a connecting tube extended along a central axis, a transmission shaft being a rigid shaft made of metal material, which is extended along the central axis and disposed in the connecting tube, a first limiting element disposed on an end of the connecting tube and formed with a first hole allowing the transmission shaft to pass there through, a second limiting element disposed on the other end of the connecting tube and formed with a second hole allowing the transmission shaft to pass there through, and a bushing. The bushing includes a main body formed with a channel extended along the central axis and several projecting parts disposed on the periphery of the main body. The bushing is located in the connecting tube and disposed between the first limiting element and the second limiting element. The transmission shaft passes through the first hole, the channel, and the second hole successively.
