The invention relates to a capacitive energy storage unit and a high voltage pulse generator. The capacitive energy storage unit comprises a conductive shell with a negative electrode leading-out end;at least two capacitors are fixedly arranged in the conductive shell; the negative electrode of each capacitor is electrically connected with the conductive shell separately, while the positive electrodes of the capacitors are correspondingly and electrically connected through positive electrode conductive parts; an insulating structure for realizing insulation between the positive electrodes andthe positive electrode conductive parts of respective capacitors and the conductive shell is placed in the conductive shell; and leading-out positive electrode via holes for allowing the positive electrode conductive parts to be led out to be conductively connected with corresponding positive electrode cables or allowing the positive electrode cables conductively connected with the positive electrode conductive parts to pass through are formed in the conductive shell. The capacitors and the positive electrode conductive parts are both positioned in the conductive shell, and the positive electrode conductive parts or the positive electrode cables electrically connected with the positive electrode conductive parts pass through the positive electrode pass-through holes to further form a corresponding coaxial structure, so that the loop inductance of a discharge loop is lowered effectively and radiation noise in the discharge process is lowered.