The invention discloses a navigation X-band radar wave group detection method based on wave theory. First, the navigation X-band radar image sequence is decomposed by empirical orthogonal functions, the main mode is selected to reconstruct the wave field, and the wave field is calibrated to obtain the observed sea area. The displacement of the wave surface at different positions in the center; for a wave surface in a radial direction, the extreme value is detected by the change of the displacement gradient, and the wave height at different positions is obtained according to the difference between two adjacent maximum and minimum values; the difference between the two sine functions And fitting the wave surface between adjacent minimal wave heights, when the fitting parameters are consistent with the wave theory, the area is identified as a wave group; combined with observations at different times, the amplitude, length and group velocity of the wave group can be obtained. The present invention first uses buoys to calibrate the main mode of the wave field to obtain wave height information of a large area in the observed sea area; based on the wave theory, two sinusoidal functions with close frequencies are used to judge the wave group, and the threshold value is not required to be selected empirically, which is simple and easy to implement , a wide range of applications and other advantages.