Dear @Li.Kang,
For the NREL 5-MW baseline wind turbine, the yield stress of the blades and tower was never specified in its specification report. But you can assume typical values for steel for the tower. For the blades, you can refer to Brian Resor’s report from Sandia National Laboratories, where the composite properties of the blades where reverse engineered–see: Structural design of the wind turbine blade - #11 by Pravin.Kulkarni.
Best regards,