The laser damage resistance of KTP crystal affects its application in the high-end solid-state laser systems. This study performed the simulation and actual experiments of laser-induced damage of KTP crystal using the laser with a wavelength of 1.064μm, a heavy frequency of 10Hz, a pulse width of 10ns and two spatially distributed beams, i.e., Gaussian beam and flat-top beam. Results indicate that the laser-induced damage thresholds of KTP crystals are 1.78 and 2.28GW/cm² respectively for the flat-top beam and Gaussian beam. The laser-induced damage experiments show that the flat-top beam causes obvious ablation morphology and cracks in the KTP crystal while the Gaussian beam causes typical nanosecond laser damage on the front of surface:pits caused by melting. In addition, the color changes in the edge of the damage region can be observed in case of flat-top beam.