The effect of radioactivity on the environment, especially on plants, has always been one of the vital researches of radio-ecology. However, long-term irradiated ecosystems are very rare. Occasionally, one special miniature ecological environment object consisted of thorium mineral (Th-232) and Tradescantia flumnensis L. over 10 years is carried out to evaluate the effect of long-term low-radioactivity gamma radiation on herbaceous plant. Several functional features of Tradescantia flumnensis L. are selected and measured with physical measurement (PM), HPGe portable gamma-ray spectrometer (HPGe PGS), wavelength dispersion X-ray fluorescence (WDXRF), and advantage isotope ratio mass spectrometer (AIR-MS). The results show that functional traits varied with the increasing of radiation dose rate. These results also indicate that the plants can adapt to low-intensity gamma radiation (<332.6 nGy•h-1) through adjustment of physical properties. In addition, low-intensity gamma radiation has positive influence on plant’s water use efficiency, growth and nutrition acquisition of roots. Restrictions on plant phosphorus demand have also been eased. However, high-intensity gamma radiation (>528.7 nGy•h-1) has exceeded the tolerance of plants, making most functional traits unhealthy or abnormal. This rare case is of great reference significance of setting biological indicators of long-term radiation system.