Abstract: It is import to study the characteristics of the spatial distribution of the underwater noise radiating from tugboat for the research and development of the detection tools in passive working mode and the underwater defense equipment. In this paper, based on the noise data obtained from the linear array under the tugboat, the spatial distribution of sound field below the tugboat is analyzed by using data processing and analyzing method from the characteristic analysis theory. The characteristic line-spectrum, continuous spectrum and total pressure level of the sound field are derived from the raw data. These are the classical acoustic curves for revealing the features of the sound field, and can be considered as important supports for the detection and recognition of tugboat-like targets.