Abstract: Nanoparticle SPION-DMSA and its radiolabeled SPION-DMSA-⁹⁹Tc^m were prepared in order to investigate the possibility of SPION-DMSA-⁹⁹Tc^m as a SPECT/MRI dual-modal imaging agent. SPION was synthesized by a hydrothermal process, and then coated with DMSA to afford SPION-DMSA. SPION-DMSA was characterized by means of various methods. SPION-DMSA-⁹⁹Tc^m was obtained by labeling with ⁹⁹Tc^m. The data of biodistribution and the SPECT and MRI images were acquired after injecting SPION-DMSA-⁹⁹Tc^m into the nude mice bearing U87MG human glioma in various intervals. The results show that SPION-DMSA exhibits super-magnetic properties. The labeling yield of SPION-DMSA with ⁹⁹Tc^m was more than 98%. SPION-DMSA-⁹⁹Tc^m is cleared from the blood quickly and has higher uptake in the liver. There was a big difference of biodistributions between SPION-DMSA-⁹⁹Tc^m and DMSA-⁹⁹Tc^m (Ⅴ) in the nude mice. The uptake of SPION-DMSA ⁹⁹Tc^m in tumor is not obvious. The results of imaging made by MRI and SPECT using SPION-DMSA and SPION-DMSA-⁹⁹Tc^m respectively show that the tumor passive targeting of SPION-DMSA and SPION-DMSA-⁹⁹Tc^m is limited. Therefore, SPION-DMSA-⁹⁹Tc^m is not an ideal SPECT/MRI dual modal imaging agent for the nude mice bearing U87MG human glioma.