Abstract: Disclosed in the present invention is a pharmaceutical composition, comprising a weight ratio of 1:120 to 1:1000 of camptothecin compound of formula I and ?-cyclodextrin or derivatives thereof, and an acidic buffer to adjust the pH=3.5-6.0. The composition can be used to treat solid tumours, such as melanoma, pancreatic cancer, hepatoma etc. The pharmaceutical composition of the present invention is miscible with a water-miscible co-solvent system in any proportion, and can be used as an intravenous infusion solvent, and has no obvious hemolysis or vascular stimulation; the pharmaceutical composition has a better tumour inhibiting rate than solubilisation of surfactants.