Alumina based rare earth oxides ceramic materials, with the good performance against the CMAS corrosion, were widely used as the thermal/environmental barrier coatings. In this work, three Y2O3–Al2O3 binary ceramic bulks, which were the Y3Al5O12, YAlO3 and Y4Al2O9, were prepared by high temperature solid state reaction using the Y2O3 and Al2O3 as the raw materials. The resistances to CMAS corrosion of these materials at 1250 °C and 1350 °C were compared fully. The compositions and structures of the samples before and after corrosion were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results showed that the different chemical compositions of the materials resulted in the different optical basicity (OB) values which can decide the reactivity of the material with the CMAS melts. The Y3Al5O12 ceramic material was inert to the CMAS for its low OB value of 0.75 and damaged seriously by the CMAS through physical penetration. The YAlO3 and Y4Al2O9 with the high OB values of 0.80 and 0.87 reacted with the CMAS to form the Ca4Y6(SiO4)6O. The YAlO3 ceramic bulk exhibited the good performance against the CMAS corrosion benefitting from the formation of the Ca4Y6(SiO4)6O and the CaAl2Si2O8.