In summary, carboxyl-abundant carbon dots (CDPAA) with a diameter of 3 nm were prepared by a hydrothermal polymerizing method. The carboxyl-abundant CDPAA were attached to the outlet of the MSNs by disulfide bonds and served as the gatekeepers to entrap drug molecules within the mesopores and the fluorescent marker tracked the carrier behavior during cancer treatment. The DOX loaded MSNs-SS-CDPAA/DOX had a relatively high drug loading up to 13.1%. The in vitro release results indicated that the prepared MSNs-SS-CDPAA/DOX exhibited redox-responsive drug release in both pH 7.4 and pH 5.0 PBS. The redox-responsive release mechanism was also studied. The MSNs-SS-CDPAA exhibited good biocompatibility and stability compared with bare MSNs. The cellular uptake result showed that MSNs-SS-CDPAA could emit blue, green and red fluorescence under different excitation wavelengths. Furthermore, MSNs-SS-CDPAA/DOX exhibited a high cellular uptake as shown by CDPAA imaging and an excellent therapeutic effect on cancer cells by MTT assay. The MSNs-SS-CDPAA nanocarriers were developed and found to have great potential for redox-responsive drug release and real-time imaging to monitor the carrier behavior simultaneously during cancer treatment.