The invention provides a polyethylene glycol modified metal organic nano material. The polyethylene glycol modified metal organic nano material is prepared from a metal organic nano material and poly-L-histidine-polyethylene glycol modified on the metal organic nano material. The polyethylene glycol modified metal organic nano material is particularly a poly-L-histidine-polyethylene glycol modified metal organic skeleton nano material and has good dispersibility, long blood circulation time and high tumor enrichment efficiency and very good water solubility and biocompatibility; the polyethylene glycol modified metal organic nano material can serve as a pure medicine carrier-free system and is applied to oncotherapy and particularly treatment of living body level, by means of tail intravenous injection, high enrichment can be achieved on the part of a tumor, and compared with the situation of directly using cisplatin, the antitumor activity is obviously improved; meanwhile, the toxic and side effects are effectively reduced, and damage cannot be caused to other parts.