A pH-responsive nanoplatform, hydroxylated mesoporous nanosilica (HMNS) coated by polyethylenimine (PEI) coupled with gadolinium and folic acid (FA) (Gd-FA-Si), was designed to deliver anticancer drug targeting and to promote contrast effect for tumor cells using magnetic resonance (MR) spectrometer. Doxorubicin (DOX) was chosen as the anticancer drug and loaded into nanopores of HMNS, then its release in simulated body fluid could be controlled through adjusting the pH. This nanoplatform could significantly enhance the MR contrast effect, and the highest theoretical relaxivity per nanoplatform could even be approximately 1.28 × 10(6) mm(-1)s(-1) because of the high Gd payload (2.61 × 10(5) per nanoplatform). The entire system possessed a high targeting performance to Hela and MDA-MB-231 cells because the FA located in the system could specifically bind to the folate-receptor sites on the surface of cell. Compared with free DOX, the nanoplatform presented a higher cell inhibition effect on the basis of cell assay. Therefore, this nanoplatform could be potentially applied as a tumor-targeted T1 MR contrast agent and pH-sensitive drug carrier system.