Tourmaline is a kind of gem material with complex structure, composition and isomorphous substitution,which resuslt in diverse types and colors of this gem. Irradiation is fairly important among the color enhancement methods of tourmaline, whose composition almost covers the whole periodic table. This paper deals with the tourmalines irradiated by 12 MeV high energy electrons. Tests on some physical properites of both untreated and treated samples were made. As a result, the authors have found that irradiation of high energy particles can cause some changes of physical properties of this gem, such as density, cell dimensions and color. One of the causes of color change is that irradiation creates and removes some crystal defects called color centers. There are two kinds of color centers, namely the electron center and the vacancy center. The actions of particles or rays on ions of Mn, Fe, Ti, Cu, Al, Si and O in OH may be probably the cause for the deep hue of some irradiatied samples. Irradiation may alter the ion valence state and its position, and hence create the color center. Irradiation also reduces the total element composition of the gem and raises its hardness. Navertheless, it only causes negligible changes on reflection indieces, and the changes of cell dimensions vary with treated colors.