A series of biotin-taxoid conjugates were designed and prepared for evaluation of their efficacy in tumor-targeting drug delivery. Recently, it has been shown that biotin receptors are overexpressed in numbers of cancer cell surface. Thus, the biotin receptor is an excellent biomarker for tumor-targeting drug delivery via receptor-mediated endocytosis. A novel disulfide-containing linker was designed and used for conjugating biotin and a taxoid, which would release the original taxoid inside of tumor cell by the action of intracellular glutathione. Three conjugates were systematically designed to verify the three stages of the whole process, i.e., internalization of biotin conjugate, cleavage of the linker, and release of the taxoid, respectively. At each stage, a fluorescent or fluorogenic moiety was recruited to visualize the progress. The syntheses of these conjugates and the cell-based evaluation of their tumor-targeting efficacy by confocal fluorescence microscopy using L1210FR cell line, which overexpresses biotin receptors, will be presented.