Abrasive flow machining (AFM) is used for processing the precision parts with inaccessible area to accomplish very high amount of surface finish and accuracy. A number of researchers have investigated to study different aspects of abrasive flow machining. In the present investigation a CFD simulation of abrasive flow machining of aluminium alloy work piece with polyborosiloxane with grease as the media and silicon carbide as abrasive particles to determine velocity distribution, pressure distribution, stress and MRR. The optimization of the process parameters has been carried out using RSM.