The invention relates to a frame extracting method for conversion from an ultrahigh-frame-frequency image flow to a standard analog video flow. A triggering signal of the standard analog video flow issynchronized with a triggering signal of the ultrahigh-frame-frequency image flow; simultaneously, the phase relationship between the triggering signal of the ultrahigh-frame-frequency image flow andthe triggering signal of the standard analog video flow is adaptively adjusted; a frame of image signal is extracted from the ultrahigh-frame-frequency image flow according to an analog video period;the conflict between an ultrahigh-frame-frequency image processing time sequence and a standard analog video display time sequence can be effectively avoided; and thus, conversion from the ultrahigh-frame-frequency image flow to the standard analog video flow is realized. The method is implemented in an engineering manner; on the premise that the ultrahigh-frame-frequency image flow processing time sequence is not influenced and hardware storage resource consumption is not increased, conversion from the ultrahigh-frame-frequency image flow to the standard analog video flow can be realized; visual observation can be conveniently carried out; and the frame extracting method disclosed by the invention has good engineering applicability.