Potassium titanyl phosphate (KTiOPO₄, KTP) possesses superior properties in several optical applications. A KTP crystal is irradiated by swift Kr^8  + ions with high energies and low fluences. The stopping and range of ions in matter code is used to simulate the energy deposition process of swift Kr^8  + ions in the irradiated crystal. The electronic and nuclear stopping power profiles of swift Kr^8  + ions irradiated on the KTP crystal are simulated, and the micro-Raman spectrum of the irradiated layer at different depths is measured by a confocal micro-Raman system. The results show that the high electronic energy loss can cause lattice damage along the ion trajectory, whereas the nuclear energy loss causes damage at the end of the ion track. The optical transmission properties of the irradiated KTP crystal are researched at visible and near-infrared bands.