Effective and specific diagnostic imaging of brain glioma remains a challenge. Magnetic nanoparticles are actively being developed as contrast agents for diagnosis of tumor. In this work, we developed the targeted magnetic nanoparticles as T₁-positive magnetic resonance imaging (MRI) contrast agents. Zn-doped Fe₃O₄ NPs were synthesized by solvothermal method, coated with liposome and conjugated to a tumor-penetrating peptide (RGERPPR). The effect of zinc doping on the magnetic properties of Fe₃O₄ nanoparticles was studied. Zn_0.4Fe_2.6O₄-PEG nanoparticles exhibited T₁ MR contrast enhancement. Cytotoxicity assay indicated that nanoparticles have good biocompatibility and low toxicity. And the in vitro cellular uptake assays on U87 cells confirmed that the conjugation of RGERPPR increased the uptake of the Zn_0.4Fe_2.6O₄ NPs. In vivo MR imaging showed the contrast enhance of U87 brain glioma in rat model after injection.