Abstract: In order to predict the aerodynamic noise of vehicle alternators more accurately, an approach based on computational fluid dynamics (CFD) and acoustic analogy theory is proposed for aerodynamic noise prediction of a vehicle alternator under the mounted condition in laboratory and considering the factors affecting acoustic propagation. The large eddy simulation (LES) method is adopted to calculate the three-dimensional unsteady flow field inside the alternator firstly. Then the surficial pressure fluctuation of rotating components is equivalent to rotating dipole sources based on Lowson's fan source theory. After that, a half free field acoustic computational model is established to predict the outer radial acoustic field of the alternator by taking the inner face of alternator enclosure as the boundary of sound sources and considering influences of the enclosure and experimental rig desk on the acoustic propagation. Finally, prediction results are validated by experiment data. It shows that there is an obvious dipole directivity of the radial acoustic field of aerodynamic noise of the alternator, and the prediction results agree with experimental ones quite well. The approach in this work can predict the aerodynamic noise of alternators more accurately. Furthermore, it provides a reference for aerodynamic noise prediction of alternators mounted on vehicles where more obstacles need to be considered.