The present work studies the Raman spectra of heavy water at pressure from 0.1 MPa to 800 MPa at ambient temperature using the method of diamond anvil cell and Raman spectrum technique. The result shows that the Raman peak of heavy water moves to lower frequency, and the linear relationship exists between Raman shift and pressure. There is no abrupt change in Raman shift, indicating that no phase transition occurs. Raman peak of heavy water is separated, corresponding to O—D vibration inside D2O molecule as the higher frequency peak and to hydrogen bond among D2O molecules as the lower frequency peak. Research on the characters of these two kinds of Raman spectra indicates that the area of lower frequency peak for hydrogen bond among D2O molecules exhibits different changes at different pressures, and the influence of pressure on hydrogen bond among D2O molecules is not unchangeable. The area of Raman spectra peak reflects the amount of vibrations which result in the Raman spectra peak, and the change in the area of Raman spectra peak reflects the change in the amount of special vibration. Because of the strong interaction between hydrogen bonds among D2O molecules, the molecules of D2O are apt to form the symmetrical dimensional structures of tetrahedron which consists of five molecules of D2O. So the biggest area of Raman spectra peak represents the most stable structure that is the symmetrical dimensional structures of tetrahedron consisting of five molecules of D2O. This result proves that the most stable structure is existent.