Abstract: The application of Resonance Radiation Theory (RRT) for submerged rectangular plates was investigated. The RRT formula of the rectangular plate was derived and validated numerically. For fluid loaded rectangular plates, the physical essence of the complex resonant frequency, and the relationship of which with residue of the reactance and modal radiation efficiency were deeply analyzed. The real part of complex resonant frequency represents the actual modal natural frequency, and the imagine part determines modal radiation ability. It is easy to find the mode whose radiation ability is relatively strong, which leads to an idea to targeted control of the sound radiation. Since the difficulty in solving complex resonance frequency by the method of searching in complex plane, an efficient method for solving complex resonance frequencies and residues of plates was presented. On the basis of the method and RRT, a tool for predicting rapidly and efficiently the radiated sound power of rectangular plates was proposed and validated numerically.