Abstract: As to the designed storage of immobile pressure vessel used to contain liquefied gas including LPG, the author presents the view different from those mentioned in《Technical Regulation for Safety of Pressure Vessel》and《Code for Design of City Gas Engineering》(GB50028-2006).The new arithmetic takes the liquid volume as a base to calculate the maximum storage, divides the proportion of the geometric volume of the liquid dimension into such three alarming grades as yellow, orange and red, and puts forward a relevant operation condition and answering scheme aiming at the three alarming grades, which ensures safety operation and increases using efficiency of the pressure vessel.