Abstract: In-situ gamma-ray spectrometer survey is carried out in Zhuhai, Guangdong province from 2002 to 2003 in order to estimate the radiation level of natural radionuclides. Measured area is more than 100 km2 and 970 sites with NaI(Tl) (φ 75 mm×75 mm) gamma-ray spectrometer. The specific activity of 40K、 238U and 232Th are 654.2±338.0, 85.7± 31.6, and 159.8±49.0 Bq·kg -1 in weathered granite, and 632.3±75.1, 35.2±14.6 and 70.2±18.6 Bq·kg -1 in the sediments, respectively. Biotite Granite is the source of 40K、 238U and 232Th in the medium on ground in Zhuhai. The specific activity of natural radionulides have significant dependence relation with geological background, such as lithology.