The utility model discloses a speed-adjustable pay-off device which comprises a pay-off frame and a drive motor. The drive motor is connected with the pay-off frame through a belt wheel and further connected with an electric controller. The pay-off device further comprises an oscillating bar type tension adjusting mechanism. The oscillating bar type tension adjusting mechanism comprises fixing plates arranged on the two sides of a bottom support respectively. Two fixing rods are arranged on the inner sides of the two fixing plates respectively, fixed guide wheels are arranged at the tail ends of the two fixing rods, and two eccentric cams and two oscillating bars connected with the eccentric cams respectively are arranged on the outer sides of the two fixing plates respectively. Position sensors are arranged under the eccentric cams, oscillating guide wheels are arranged at the tail ends of the two oscillating bars, and a cylinder component is further arranged between the oscillating bars. Compared with the prior art, the speed-adjustable pay-off device can adjust the pay-off speed, meet the requirement for the pay-off speed in the constructing process, and prevent electric wires from being damaged to the greatest extent.