The technique of sampling-image streaking frame for plasma diagnostics in ICF is presented. Theoretical analysis of this technique, including its exposures time, framing rate and spatial resolution is given. A specially designed streak image tube, together with an active-passive mode-locked YAG laser is used to make a preliminary proof-of-principle experiment. And by means of digital image processing the experiment result gives 16 frames with an exposure time of better than 6.3ps and spatial resolution of 3.5 lp/mm in the photocathode.