ZrSiO 4 bulk was prepared by pressureless sintering process and ZrSiO 4 coating was deposited on the SiC f/SiC substrate using air plasma method. The microstructures of ZrSiO 4 bulk and ZrSiO 4 coating are both dense. A preliminary study of a water vapor corrosion test for ZrSiO 4 bulk and ZrSiO 4 coating was performed under the conditions of 1.013×10 5 Pa, 90%H 2O/10%O 2, 1300 ℃, and low gas velocity. Results show that some pores appear on the surface of the ZrSiO 4 bulk. The main crystal phase is ZrO 2 and the weight loss of ZrSiO 4 bulk is only 0.236 mg/cm 2 after corrosion. The ZrSiO 4 coating peels off from the substrate after 109 h. The number and intensity of diffraction peaks of ZrO 2 in the coating increase, and the major crystal phase of the coating is still ZrSiO 4. A porous microstructure accompanied with cracks is observed on the surface of ZrSiO 4 coating after corrosion.