The vibration of a blade of the large horizontal axis wind turbine in the rotating plane was investigated. The blade was simplified as an Euler-Bernoulli beam, which rotates constantly around fixed axis and has constant section, while the length of the blade is much larger than the chordal length of the section. The aerodynamics force model was established by the blade element momentum theory with a tip loss correction. The experimental aerodynamics data reported for the aerofoil of NACA63-B series were fitted first to express the coefficients as the function of the attack angle. A further analysis indicates that if the blade is simplified as an Euler-Bernoulli beam, which rotates constantly around fixed axis and the attack angle is restricted in the region from -10 to 30 degree, the aerodynamics force coefficient may be approximate to zero in the vertical or tangential direction for the blade with tip loss correction. This leads to peaked points on the aerodynamics force curve, which is reasonless in the sense of physics. Such a conclusion may be useful in the design and nonlinear vibration analysis of blades of a large wind turbine.