Few studies have paid attention to high-concentration controlled release potassium (CRK) fertilizer because conventional potassium chloride (KCl) particles with the characteristics of irregular, high specific surface area, and bad fluidity are generally unsuitable to produce controlled-release fertilizer. The objective of this study was to investigate the interacting effects of urea-formaldehyde and additives on KCl granulation. In addition, the controlled-release characteristics of CRK based on modified KCl particles were determined in our research. Results indicated that 4-8% urea-formaldehyde combined with 6-8% bentonite was used as a double binder to increase the granulation rate, smoothness, and particle hardness of KCl granules, which enhanced its characteristics for the coating process. The K release rates of modified KCl particle-based CRK were significantly lower than that of the conventional KCl particle. In conclusion, the novel KCl granulation technology has an enormous potential for large-scale applications to satisfy the increasing demand for CRK fertilizers in the future.