Using both tomography emission spectroscopy and actinometry measurements on reduced-pressure oxygen ICP, the ground and excited-state densities of oxygen atoms were observed with spatially resolved profile, and the electron temperature, density, and dissociation degree of oxygen molecule were measured in a spatially resolved manner by applying a self-consistent oxygen atom collisional radiative (CR) model solution. The electron temperature and degree of dissociation were high in the center, while the electron density was low in the center. This finding can be attributed to the presence of O- ions as negative charges in the central region of the plasma chamber.