The short-lived radioactive nuclide in rainwater were measured using general radioactive measurement instrument and studied in this paper. The experimental results indicate that there are short-lived radioactive nuclides in all kinds of rainwater. The result of gamma ray spectrum analysis shows that these short-lived radioactive nuclides are 218 Po

214 Pb

214 Bi and so on. The entry mechanism of these radioactive nuclides into rainwater are discussed. These radioactive nuclides enter rainwater during the course of vapor condenration and raindrop incorporating and scouring the air. These radioactive nuclides in rainwater have an effect on the radioactivity measurement such as ground gamma measurement

210 Po measurement and so on.