Abstract: The thick disk radiator is a good choice for high power and high frequency sound radiation because of high mechanical strength and small lateral size. The sound field characteristics radiated by the flexural vibration of thick disk are studied based on Mindin theory. Numerical expression of the sound field directivity for thick circular plate under three boundary conditions is derived and its sound radiation characteristics are studied with the compiled program. Results show that the directivities of the same size thick disk under different boundary conditions are different:under the fixed boundary condition the sound radiation directivity is the best, and the next under the simply supported boundary condition, the worst under free boundary condition; moreover, with the increase of the thickness, under different boundary conditions the main lobes of the radiation sound field all become sharper, and correspondingly the sidelobes increase gradually, thus the directivity becomes more and more complex. For the thick disk of the same frequency, the material has little influence on its directivity; however, for the thick disk of the same size, the material has a great influence on its directivity. The results provide a reference for the practical application of the thick disk flexural vibration radiator.