KDP/DKDP crystal has the advantages of simple growth method, low cost and good optical properties, while the oversized KDP/DKDP crystal is the only single crystal material that can be used in high power laser engineering. However, there are many factors in the process of crystal growth, and the post-treatment of crystal will also affect the performance of crystal, which is directly related to the practical application of oversized KDP/DKDP crystal. Accordingly, this paper reviews the important research progress of oversized KDP/DKDP crystals in recent years, especially for the traditional growth and rapid growth problems and the corresponding countermeasures as well as the properties-related of research, and the transmittance, deteration level and laser-induced damage of oversized KDP/DKDP crystals are analyzed and discussed with key point.