Potassic rocks are aluminosilicate crystals containing abundant potassium elements, which could be used to produce K-fertilizers by extracting K+, synthesizing zeolites, and preparing valuable industrial products. To realize the efficient utilization of potassic rocks, the sub-molten salt method was used to activate potassic rocks using NaOH-NaCl as the activating agent. The effects of the addition of NaOH, NaCl, and H2O on the leaching rate of K+ were investigated, respectively. The raw materials, activated products and filtration were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and titration method. The experimental results showed that the optimal activation conditions are m(NaOH)/m(potassium rocks) of 0.7, m(NaCl)/m(potassium rocks) of 0.7, m(H2O)/m(potassium rocks) of 1.0, activation temperature of 160℃, and activation time of 120 min. The leaching rate of K+ could reach about 92%, and the alkali concentration was decreased to 41wt%. Comparative investigations were made with the effect of activation of potassic rocks using the NaOH sub-molten method concerning the leaching rate of ions of K+, SiO32- and Al3+ and activated products in the identical reaction conditions. The concentrations of K+, SiO32- and Al3+ in the mother liquor obtained from NaOH-NaCl sub-molten system were significantly increased in contrast with that from the system in the absence of NaCl, demonstrating the promotion effect of NaCl for the activation of potassic rocks and the peaks assigned to SOD zeolite were greatly intensified with the introduction of NaCl. Compared with the activation effect and conditions of other additives in the sub-molten salt method reported in the literature, NaOH-NaCl sub-molten system exhibited a satisfactory leaching rate of K+ under the condition of significantly decreased alkali concentration at a low temperature (160℃) for short time (120 min), which greatly reduced energy consumption and time wasting. According to the compositions of mother liquor after sub-molten salt activation, the circulating process for the activation of potassic rocks in the NaOH-NaCl mixed sub-molten salt system was designed to realize the recycling of NaCl. This work provides an energy-saving and effective method for the activation of potassic rocks, paving a new way to realize the comprehensive utilization of potassic rocks.