NaCl ceramics were prepared by room-temperature cold sintering using moistened NaCl powder with 4wt% water and dry pressing using dehydrated powder. When the applied uniaxial pressure is low, the relative density of dry-pressed NaCl ceramic is significantly lower than that of cold-sintered ceramic, while the former is 98.5%-99.3% and much higher than the latter (94.3%-94.6%) for high applied pressure of 200-300MPa. The uniaxial pressure-induced plastic deformation dominates the densification of dry-pressed NaCl ceramic, and also plays a role during cold sintering as well as the dissolution-precipitation process. The lower density of cold-sintered NaCl ceramic under high applied pressure is attributed to the trapped water in ceramic body during cold sintering. Besides, the presence of water always promotes the microstructural homogeneity, which is responsible for the much higher Qf value of cold-sintered NaCl ceramic. The optimal microwave dielectric properties with epsilon(r)=5.55, Qf=49600GHz, and (f)=-173ppm/degrees C are obtained in cold-sintered NaCl ceramic under the applied pressure of 300MPa, indicating that it is a promising candidate as a microwave dielectric material.