The wind power generation by wind turbines has been developed rapidly in recent years. However, the noise generated by wind turbines is also widely attracted the focuses of the people. The large wind turbine acoustic tests were conducted by acoustical transducers measurement in far field, and the main noise sources area and their generation mechanism were investigated. The results show that there existed high noise level in downstream and blade plain directions of wind turbine, and also the tone frequency and integer multiples of this frequency were found, which indicated that the aeroacoustic noise in trailing end of blades and mechanical noise after the wind wheel were the main noise sources. Some effective methods to control those noise sources were presented finally.