Abstract: An underwater ambient noise data acquisition system based on virtual instrument and LABVIEW is presented in this paper. The system uses the portable data acquisition card NI USB-9215A as the core hardware,combinating the virtual instrument technology and the graphical programming language LabVIEW,to complete the data acquisition functions. Signal conditioning circuit was designed to pre-amplify and filter the underwater ambient noise signals. This circuit includes two parts,one is the pre-amplifier and the other is the low-pass filter. Finally,the system implemented one-third octave analysis based on Matlab to get the one-third octave spectrum of measured underwater ambient noise.