The invention discloses a method for eliminating the influence of rainfall on sea wave observation by an X band wave radar. The method comprises two parts, in the first part, the positions of a peak and a trough are extracted from the main mode of a wave field, and n the second part, the intensity value of the peak is extracted from an original radar image. A problem that the X band wave radar can not observe sea wave information in a rainy day in the prior art is solved, and a guarantee is provided for offshore activities and the safe navigation of ships in the rain.