A freeze-dried hydroxy camptothecin powder injection for treating primary liver cancer, gastrointestinal cancer, vesical cancer, lung cancer, leukemia, etc is prepared from hydroxy camptothecin, aminoacetic acid, lactose, sodium hydroxide and the water for injection through preparing buffer liquid from sodium hydroxide, aminoacetic acid and the water for injection, dissolving hydroxy camptothecinin it to obtain solution A, dissolving lactose in the water for injection to obtain solution B, adding A and rest of aminoacetic acid to B, stirring, regulating pH value, adding water for injection, filtering loading in containers, freeze drying and sealing.