The present invention relates to a slightly acidic environment-sensitive and ketal-linked gefitinib axially substituted boron subphthalocyanine complex and a preparation method therefor and a medical use thereof. In particular, the present invention relates to a boron subphthalocyanine-gefitinib complex as shown in general formula (I) and a preparation method therefor and a pharmaceutical composition containing the complex, and the use thereof as a photosensitiser, especially the use in the treatment of cancers, wherein the definition of each substituent in general formula (I) is the same as that in the description. In a normal tissue environment, due to the interplay between the boron subphthalocyanine group and the gefitinib group, the complex has a lower cytotoxicity. However, in the extracellular slightly-acidic environment of tumour tissue, ketals hydrolyse and the fragments of the hydrolysate, i.e. boron subphthalocyanine, exhibit an extremely high photosensitive activity, while a gefitinib derivative obtained by hydrolysis can be used as an inhibitor of epidermal growth factor receptor (EGFR) tyrosinase for inhibiting tumour growth. The complexes can be prepared into photodynamic therapeutic and chemotherapeutic double-efficacy anticancer drugs targeting both the tumour extracellular slightly-acidic environment and the EGFR tyrosine kinase.