Environmental radioactivity is produced by radioactive materials in the human environment. While some radioisotopes, such as strontium-90 (⁹⁰Sr) and technetium-99 (⁹⁹Tc), are only found on Earth as a result of human activity, and some, like potassium-40 (⁴⁰K), are only present due to natural processes, a few isotopes, e.g. tritium (³H), result from both natural processes and human activities. The concentration and location of some natural isotopes, particularly uranium-238 (²³⁸U), can be affected by human activity because of the constant exposure of Human beings to radiation caused by terrestrial, extra-terrestrial and anthropogenic radio nuclides, it is necessary to determine and estimate the activity of various radio nuclides in environmental media such as vegetation, soil, and water. In the present research, the activities of ²²⁶Ra, ²³²Th and ⁴⁰K are measured in soil, vegetation and water samples, collected from Yangdong District, Yangxi County, and Yangjiang County of Guangdong Province, China using an HPGe based gamma spectrometry system. The measured mean activity of ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples was found to be 31.19 ± 1.2, 47.00 ± 2.30 and 589.31 ± 17.52 Bqkg^-1, respectively. The measured mean activity of these radionuclides in all water samples was found to be below minimum detectable activity. The measured mean activity of ²²⁶Ra, ²³²Th and ⁴⁰K in vegetation samples was 19.92 ± 3.09, 25.36 ± 8.11 and 4982.94 ± 85.68 Bqkg^-1, respectively. No anthropogenic ¹³⁷Cs was detected in these environmental samples. Mean radium equivalent activity (Raeq), external radiation hazard index (Hex), internal radiation hazard index (Hin) and absorbed dose rate (D) for the area under study were determined as 142.92 Bqkg^-1, 0.38, 0.47 and 66.47 nGyh^-1, respectively. The annual effective dose equivalent (AEDE) varied in the range from 0.03 to 0.12 mSvy^-1. It is concluded that the surveyed area do not pose any significant radiological risk to the population and environment.