<p>For a long-distance guard radar, MTI filter usually employs low staggered pulse repetition frequencies (PRF) modulation technique to overcome blind speed and detect the targets at low altitude in the presence of clutter. For a given ratio of the maximum-to-the minimum period ( r ), we find that there exists an optimum stagger ratios construction criterion (OSRCC) which can guarantee the first null depth minimum, and the associated estimation formula containing variable  has been derived successfully. In addition, based on a better understanding of the properties of staggered PRF, we introduce a new stagger ratios optimization method that is much simple, efficient and flexible. In brief, this paper has deconstructed this technique.</p>