The microscopic structure characteristic of low frequency sound propagation in shallow water is that a stable space-frequency interference structure represented by waveguide invariant exists. Both the scalar field and the vector field determine all the features of the acoustic field. The vector field characteristics of space-frequency interference structure in shallow water acoustic field are investigated. The theoretical analyses of the mechanism of interference structure in the sound pressure spectrum, the kinetic energy density spectrum, and the acoustic intensity flow spectrum in shallow water vector acoustic field are conducted, the numerical simulation studies of the interference of the Pekeris waveguide in energy and energy flow density characteristics are performed, and the sea trials for broadband sound source radiation vector sound field interference properties and characterization are also carried out. The experimental results accord with the theoretical analyses and simulation results very well. The research results show that stable space-frequency interference structure in acoustic vector field exists in many forms for modal coherent in short-distance and long-distance. In addition to various forms of energy and energy flux density spectra, in coherence-coefficient spectrum there appear the interference characteristics. These forms of space-frequency interference structure can be described by waveguide invariant theory effectively.