Abstract: To analyze the sound radiation characteristics of a periodic stiffened plate,an efficient method to calculate the far field radiated sound pressure from the stiffened fluid-loaded plate excited by a time-harmonic point force is present. In this approach,the vibro-acoustic equation of the coupled system,the bending and torsional motion equation of the stiffeners,acoustic wave equation and the fluid-structure coupled condition in physical space are firstly transformed to the wavenumber domain by using the Fourier Transform method.By solving these equations together,yields an infinite set of algebraic coupled equations about the transversal displacement of the plate in wavenumber domain,which is numerically solved by truncating them in a finite range.At last,combining with the stationary phase method,the far field radiated sound pressure can be calculated.Validation of the present method is performed by comparing the present predictions with that given by existing method,perfect agreements are achieved.The influences of the excitation locations,thickness of the plate,the periodicity spacing and width of the stiffeners on the sound radiation characteristic of the periodic stiffened plate is numerically quantified and conclusions of significant practical implications are drawn.