Structural stability of KH<sub>2</sub>PO<sub>4</sub> (KDP) crystal under laser irradiation is a great challenge to nonlinear optical devices. Herein, the dependency of structural stability on the propagated laser wavelength was established. Separated precipitations with different morphologies, including irregular fusion, elongated prism, and quasi-equiaxial particles were irradiated from the KDP crystal surface by a laser with different wavelengths, including 0.103, 355, and 785 nm. All the precipitations induced by laser irradiation were identified to be the same KDP phase as its parent phase examined by electron diffraction. Noticeably, the stacked periodicity degree at (001) planes of precipitations becomes irregular somehow. It is believed that our research findings might have new implications and inspirations in constructing KDP devices with better stability.