The invention provides a three-dimensional forward-looking audio-visual 
sonar (3DFLS) 
system and method. The 3DFLS 
system comprises a 
sonar cabin, an emitting 
linear array, a receiving array and a 
data processing module; the emitting array changes the vertical emitting aperture to adjust the vertical emitting wave beam width, and thus the shallow 
water environment is detected; the receiving arraycomprises multiple 
layers of receiving arc arrays, the interlayer spacing is same, a plurality of receiving elements are distributed in each layer of receiving arc array at equal intervals, and the receiving arc arrays adhere to the bottom of the 
sonar cabin; and the 
data processing module is arranged in the sonar cabin and used for 
processing detection data of the emitting array and the receivingarray. The method comprises the steps that the emitting array sets an emitting wave beam through the 
data processing module and process the emitting wave beam stably, the receiving array processes echo data, coordinates of scattering points in a three-dimensional space are calculated, and three-dimensional acoustic imaging is obtained. An emitting scheme capable of adjusting the wave beam width is adopted, different 
water body environments are adapted more excellently, thus the detection effect of the 3DFLS is improved, and adaptability to the environment is improved.