A pitch varying device for a wind turbine blade, configured to control a pitch angle of a blade rotatably mounted on a hub , and the blade being mounted on the hub through a pitch bearing , and the pitch varying device for the wind turbine blade comprises: a disc-type driving structure fixedly mounted on the blade and being perpendicular to an axis of the pitch bearing , wherein a track surrounding the axis of the pitch bearing is provided on the disc-type driving structure ; a first linear telescopic driving mechanism having one end hinged to the hub and another end connected to the track through a first clamping member capable of clamping the track , wherein the first linear telescopic driving mechanism and the first clamping member are connected through hinge connection; and a second linear telescopic driving mechanism having one end hinged to the hub and another end connected to the track through a second clamping member capable of clamping the track , wherein the second linear telescopic driving mechanism and the second clamping member are connected through hinge connection; wherein in a case that an included angle between a target pitch angle and a present pitch angle is greater than a preset threshold, the second linear telescopic driving mechanism is configured to drive the disc-type driving structure ; and in a case that the included angle is smaller than or equal to the preset threshold, the first linear telescopic driving mechanism is configured to drive the disc-type driving structure . a disc-type driving structure fixedly mounted on the blade and being perpendicular to an axis of the pitch bearing , wherein a track surrounding the axis of the pitch bearing is provided on the disc-type driving structure ; a first linear telescopic driving mechanism having one end hinged to the hub and another end connected to the track through a first clamping member capable of clamping the track , wherein the first linear telescopic driving mechanism and the first clamping member are connected through hinge connection; and a second linear telescopic driving mechanism having one end hinged to the hub and another end connected to the track through a second clamping member capable of clamping the track , wherein the second linear telescopic driving mechanism and the second clamping member are connected through hinge connection; wherein in a case that an included angle between a target pitch angle and a present pitch angle is greater than a preset threshold, the second linear telescopic driving mechanism is configured to drive the disc-type driving structure ; and in a case that the included angle is smaller than or equal to the preset threshold, the first linear telescopic driving mechanism is configured to drive the disc-type driving structure . in a case that an included angle between a target pitch angle and a present pitch angle is greater than a preset threshold, the second linear telescopic driving mechanism is configured to drive the disc-type driving structure ; and in a case that the included angle is smaller than or equal to the preset threshold, the first linear telescopic driving mechanism is configured to drive the disc-type driving structure . <EOS>