The Si-doped Ce-Zr-O solid solutions have been prepared by the reverse microemulsion method. The effects of Si and its content on the structure characters, thermal-stability and reducibility of the Ce-Zr-O solid solution have been studied by N-2 adsorption, XRD, laser Raman (LR), TPR, FT-IR, NMR and XPS methods. The results indicate that, there are the bonds of Si-O-M (Ce or Zr) in the Ce-Zr-Si-O solid solutions, and the presence of Si can increase obviously the surface area, thermal -stability, crystal lattice distortion rate, and reducibility of the solid solution. The surface area of the sample with 20 wt.% Si reaches 153 m(2) g(-1) after being calcined at 900 degrees C for 6 h. The Ce-Zr-O solid solution with 5.2-10 wt.% Si shows excellent thermal -stability and reducibility. (C) 2007 Elsevier B.V. All rights reserved.