Prussian blue and its analogs (PBAs), which possess an open framework structure that is beneficial for ion storage and diffusion, have demonstrated significant potential as cathode materials for next-generation non-lithium batteries, such as Sodium Ion Batteries (SIBs) and Potassium Ion Batteries (KIBs). However, most of the PBAs are imperfect with structural defects and crystal water, which cause the electrochemical performance to be far from ideal and unsuitable for industrial application. In this review, firstly, the origin of defects in PBAs has been elucidated comprehensively from the aspect of nucleation and growth. Subsequently, the effective strategies to eliminate these defects are thoroughly summarized and discussed. We hope that the present review would stimulate more fundamental thoughts on the growth of defect-free PBAs crystals and put forward new insights into reducing defects in various aspects, promoting the practical applications of PBAs in SIBs and beyond.