Experiments and simulations were performed to investigate the characteristics of staining on pad surface. Experiments were performed on a table-top axisymmetric polishing system, consisting of a 12-inch non-rotating platen and a 4-inch rotating wafer carrier having the same center axis. Results showed that the stain deposited on each land area was found to be darker in the direction of wafer rotation and in the radial direction, suggesting that staining agent was produced by mechanical action during polishing and was advected downstream by the slurry flow. Generally, staining increased with polishing pressure, wafer rotation rate and polishing time. The simulated slurry velocity showed shear flow on the land areas and wafer-driven circulation in the grooves. Thermal model simulation showed 12 degree temperature rise on the reaction at the surface of wafer.