Due to its superior mechanical, processing, and service properties, oxide dispersion-strengthened (ODS) alloy (particularly Fe base ODS steel) has emerged as the most promising future candidate for advanced reactor structural materials. However, there are some problems with hot isostatic pressing sintering ODS steels, such as higher sintering temperature, longer sintering time, and relatively coarse grains. In this work, 14Cr-ODS steels were prepared by ultra-high pressure sintering with a sintering pressure of 3, 4, and 5 GPa, respectively. The microstructure and mechanical properties of the ultra-high pressure sintered 14Cr-ODS steel samples were characterized by density test, SEM, TEM, hardness test, and tensile test. Based on the contrast analysis of microstructure and mechanical properties, the effect of sintering pressure on the microstructure and mechanical properties of ultra-high pressure sintered 14Cr-ODS steel was investigated, and the effect mechanism was thoroughly analyzed. Analysis results show that the main oxide precipitate of ultra-high pressure sintered 14Cr-ODS steel is Ti2O3, and the average grain size of 14Cr-ODS steel prepared by ultra-high pressure sintering is less than 300 nm, which is approximately 5% of the average grain size of 14Cr-ODS steel prepared by conventional hot isostatic pressing sintering. The average grain size of samples prepared by ultra-high pressure sintering decreased initially and then increased as sintering pressure increased. The Vickers hardness of ODS steel samples sintered at 4 GPa can reach 604 HV, and the tensile strength is approximately 1.5 GPa, which is 1.6 times than that of 14Cr-ODS steel samples with a similar composition prepared by conventional hot isostatic pressing sintering. Ultra-high pressure sintered 14Cr-ODS steel with good sintering formability and a density greater than 99% can be obtained at lower sintering temperatures and shorter sintering times. Its excellent performance can be mainly associated with the comprehensive influence of the plastic deformation effect produced by ultra-high pressure sintering on grain nucleation and atom diffusion in sintered samples.