A spark plasma sintering (SPS) process has been explored to densify FJS-lunar soil simulants for structural applications in space explorations. The effect of SPS conditions, such as temperature and pressure, on the densification behavior, phase transformation, microstructural evolution, and mechanical properties of FJS-1 have been examined by conducting the X-ray diffraction analysis, electron microscopy imaging, and nano/micro indentation testing. Test analysis results were also compared to results from the FJS-1 powder and sintered samples without pressure. The FJS-1 powder was composed of sodian anorthite, augite, pigeonite, and iron titanium oxide. When FJS-lunar soil simulants were sintered without pressure, the main phase evolved from sodian anorthite to the intermediate sodian anorthite, jadeite and glass, and iron titanium oxide at 1000 degrees C, which were further transformed into filiform and feather-shaped augite and schorlomite at 1100 degrees C. Most densification processes in pressureless sintering occurred at 1050 degrees C-1100 degrees C. During the SPS process, the main phases were sodian anorthite, pigeonite, and iron titanium oxide at 900 degrees C. These phases were transformed to sodian anorthite, glass, and feather-shaped augite at 1000 degrees C and 1050 degrees C, with the nucleation of dendritic schorlomite at 1050 degrees C. Significant densification by SPS can be observed as low as 900 degrees C, which indicates that the application of pressure can substantially lower the sintering temperature. The SPSed samples showed higher Vickers microhardness than the pressureless sintered samples. The mechanical properties of the local phases were represented by the contour maps of elastic modulus and nanohardness. Multiscale mechanical test results along with the microstructural characteristics further imply that the SPS can be considered a promising in-situ resource utilization (ISRU) method to densify lunar soils.