Abstract: The present invention relates to the field of pharmaceutical synthesis, and in particular to an antitumor heterocyclic imidazole compound (I), namely: a pharmaceutical salt of 4-(3-(4-(1H-imidazo[4,5-b]pyridine-5-yl)piperazine-1-carbonyl)-4-fluorobenzyl)phthalazine-1(dihydro)-ketone, a preparation method therefor, a pharmaceutical composition thereof and a use thereof in the preparation of antitumor drugs. The pharmaceutical salt of the compound (I) in the present invention may be used in the preparation of a medicament for the treatment or prevention of conditions which can be improved by inhibiting PARP activity.