Abstract: According to the interference of acoustic vector field in a Pekeris waveguide of shallow water environment,it analyzes the formation mechanism of sound intensity spectrum,particle vibration velocity spectrum,complex sound intensity spectrum and waveguide impedance spectrum interference structure based on the Normal Mode Theory,explores the waveguide invariant representations of interference structure in frequency-range domain,and conducts a sea-trial for interference structure with a broadband radiated source.Both the simulation research and the analysis of seatrial data indicate that,in frequency-range domain,the above four kinds of physical quantities will exhibit a stable interference structure which can be represented with waveguide invariant β,and the interference components of complex sound intensity will better reflect the interference characteristics of the waveguide.Finally,a multi-scale linear filter is introduced for image processing of LOFAR gram which measured in sea-trial,the processing results show that the proposed filter can effectively enhance the interference characteristics,and conductively detect and extract striations' information from interference structures.