[en] During September 8th to October 7th in 2012, an airborne gamma-ray spectrometric survey was implemented to investigate the environmental radiation background around the Sanmen NPP. This survey covered an area of 7192 km² and collected 99577 sets of data, with which the environmental radiation background measurements and activity concentrations of natural Potassium-40, Uranium-238 and Thorium-232 around Sanmen NPP were calculated. It is the conclusion that the dose rate of northwest area around Sanmen NPP is high, southwest and northeast is relative high, and the central area is low. No resoluble manmade radionuclide or any lost radioactive sources was identified. Two airborne radiation hot-point's were identified, which are aroused by higher natural radiation in geological environment. (authors)