An on-site, rapid, measurement-based, radiation-distribution visualization system with radionuclide recognition was developed for quick decision making during a radiation emergency. After scanning of the area was complete, radionuclide-specific radiation-distribution contours were displayed in two and three dimensions on a map of the measurement area, in a few tens of seconds, by clicking once on an execution file, which was programmed using MathWorks' MATLAB software. The contours were fundamentally verified using Cs-137 and Co-60 standard sources. Radiation distribution in the measurement area was simultaneously displayed in the main office using code division multiple access. It was demonstrated that rapid decision making for public safety is possible through the prompt display of radiation distribution in a nuclear emergency environment. This can also be applied to establish an environmental restoration plan for decontamination and decommissioning of nuclear power plants.