The problem of electromagnetic (EM) scattering between the time-varying lossy dielectric ocean and a moving target is always solved by using some numerical algorithm. However, the elements of the impedance matrix and the surface electric and magnetic currents of the lossy dielectric ocean must be determined and evaluated again at different moments due to the varying of the ocean with time, and the numerical algorithm will produce an enormous amount of calculation. To overcome this shortcoming, the reciprocity theorem is used to solve the coupling field between a time-varying lossy dielectric ocean and a moving conducting plate above it. Due to the advantage of the reciprocity theorem, the difficulty in computing the secondary scattered fields is reduced. The polarization currents of the ocean and the first scattered field from the conducting plate are both evaluated by using the physical optics (PO) method. The backscattered field from the ocean is evaluated by using the Kirchhoff approximation (KA) method. The characteristics of the coupling backscattered field and the Doppler spectrum are analyzed in detail for different incident conditions.