Abstract: The two -dimensional standing wave figures of an annular plate (Chladni patterns)as the inner boundary is clamped，are investigated experimentally and theoretically. It is found that the Chladni patterns can be precisely controlled by adjusting the frequency and position of the vibration source. Two kinds of patterns have been observed，one kind only has radial nodal lines (excepting the inner boundary)and the other has both of radial nodal lines and circular nodal lines. Furthermore，the radii of the circular nodal lines，the change rules of the eigen values，and the elastic modulus of the thin plate have been obtained. The results of experiments are consistent with the analytical solutions.

Key words: FANG Yizhong, SHEN Han, WANG Gang, CUI Xintu, LIAO Deju, FENG Raohui