Wind energy is one of the promising alternative energy resources after solar and hydropower. Most of wind turbine technologies are designed at high speed, whereas, not effectively operated in low wind speed areas. An effective technology is required to enhance the possible use of wind energy at low wind speeds. Diffuser Augmented Wind Turbine (DAWT) has been used recently to improve the use of wind turbine in a low wind speed area by manipulating the wind speed. The main concept of this technology is the pressure difference between inside and outside of DAWT which is occurred, hence, it might enhance the wind velocity and the power is increased as well. In this paper, simulation using ANSYS was conducted to investigate the performance of Horizontal Axis Wind Turbine (HAWT) in low wind speed area applying DAWT by modifying the angle and the length of diffuser. The variation of the diffuser angle was in the range 4-16o at L=1.25D. The simulation results showed a good agreement with the reference literature which obtained the increased power around 1.4-2.9 times higher than the non-diffuser wind turbine. The parameter of diffuser length was also investigated at L=0.25D-2.5D, with the significant impacts are obtained until L=1.25D