Magnetic iron oxide coated in hydrogenation silica (Fe3O4@HSiO2) is constructed as both a tumor drug carrier and a magnetic resonance (MR) contrast agent. Colchicine (COLC) is loaded in Fe3O4@HSiO2 with the highest amount of 28.3 wt% at pH 9. The release performance of COLC can be controlled by pH, as the porous HSiO2 shell can partially shed at pH below 3.0 to facilitate the release of COLC. MR imaging (MRI) tests prove that Fe3O4@HSiO2 at pH 3.0 (H+-Fe3O4@HSiO2) shows a stronger MR contrast enhancement than Fe3O4. Cytotoxicity experiment indicates that Fe3O4@HSiO2 has excellent biocompatibility and magnetic targeting performance. Additionally, COLC-loaded Fe3O4@HSiO2 (Fe3O4@HSiO2–COLC) displays a higher inhibition effect on tumor cells under a magnetic field than free COLC. The visibility upon MRI, high targeting, and pH-controlled release characteristics of Fe3O4@HSiO2–COLC are favorable to achieve the aim of reducing side effects to normal tissues, making Fe3O4@HSiO2–COLC an attractive drug delivery system for nanomedicine.