The invention discloses a reduced responsive 
drug-
drug conjugate preparation method which is characterized in that the method includes the steps: preparing a 
camptothecin intermediate (CPT-SS) containing a reduced responsive bond; preparing a reduced responsive 
drug-drug conjugate (GT-CPT) or (BT-CPT). The reduced responsive drug-drug conjugate has advantages of a small-molecule 
prodrug and a nano-drug, the uploading capability of the reduced responsive drug-drug conjugate can be effectively improved, the reduced responsive drug-drug conjugate solves the problems of targeting delivery of a current small-molecule 
prodrug delivery system and 
controlled release of drug selectivity, and accurate diagnosis and efficient treatment of tumors are facilitated. 
Gemcitabine (drug) and 
biotin (target)molecules are introduced, 
fluorescence of drug molecules can be temporarily shielded, the conjugate is combined with specificities of 
cancer cells, so that nano-micelles are disassembled and assembled, the 
fluorescence of the drug molecules can be reduced, and a drug releases drug properties 
under stimulation response, so that accurate diagnosis and treatment of cancers are combined.