In recent years, CMP (Chemical and Mechanical Polishing) greatly has taken its role as technology of planarizations to produce multi-level inter-connections. While slurry is flowing on a polishing pad in CMP, the polishing pad is in contact with the wafer to polish the wafer surface. Grooves are expected to supply slurry evenly, and to remove wasted particles. Our study aims at developing the design of the best patterns of grooves. By predicting slurry flows between wafers and polishing pads in CMP using CFD, the influence of the slurry flow by the grooved pad can be analyzed. In this paper simulations were carried out for cases without groove, with circular grooves and radial grooves. With analysis of the flow field, how grooves affect the velocity distributions are studied. We also simulated the replacement of old slurry to new slurry, and the roles of the grooves are discussed.