This paper presents an aerodynamic analysis of a three-bladed wind turbine using unsteady Blade Element Momentum (BEM) method. A MATLAB code has been written to perform the analysis in which a simulation model for a wind speed acting on a wind turbine rotor plane was used considering the effect of wind shear and tower shadow. Results obtained from the analysis have proved that tower shadow and wind shear contribute to periodic fluctuations in loads and mechanical power of a wind turbine .The frequency of the periodic fluctuations is n times the blade rotational frequency p, where n is the number of blades. For three- bladed wind turbine, this inherent characteristic is known as 3p effect. Furthermore, as the aerodynamic loads change periodically due to wind shear and tower shadow, this may have a large effect on output power quality and fatigue life of the blade. Hence, the loads analysis in this paper may be applicable to the improving power quality and design analysis of the wind turbine.