Abstract: A virtual surface source method is proposed to solve the problem of low accuray in the calculation of the sound field using the virtual point source method. Based on the boundary conditions of the flat plate, the surface vibration velocity of the structure is determined using modal expansion method. Based on the principle of wave superposition, the sound field radiated by the flat plate is equivalent to the superposition of the continuous distributed virtual surface source radiation sound field in the space on one side of the flat plate, and the virtual surface source is discretized using interpolation shape function. On this basis, according to Euler's theorem, a relationship equation between the surface acoustic source node and the structural surface vibration velocity is constructed to determine the virtual surface acoustic source intensity and calculate the acoustic radiation characteristic parameters. Taking a simply supported rectangular plate on an infinitely large baffle in water as an example, the calculation results of the proposed method are compared with those of the conventional virtual point source method, and the sensitivity of acoustic parameters to the number of virtual surface sound sources is discussed. The results indicate that the proposed method has higher computational accuracy compared to traditional virtual point sound source methods, and can accurately predict the radiated sound power of structures with fewer equivalent sources at the low frequenciy band.