The work aims to study the corrosion behavior of CMAS corroding barium silicate at high temperature. Firstly, high purity Er2SiO5 and Er2Si2O7 powders were synthesized by solid state reaction. Er2SiO5 and Er2Si2O7 bulks were sintered. CMAS with 35 mol.% CaO-10 mol.% MgO-7 mol.% Al2O3-48 mol.% SiO2 was coated on the surface of the sintered barium silicate bulks. Coated bulk materials were heated at 1300 ℃ and held for different times. The phase compositions of the corrosion products and the microstructures of the bulks after corrosion were analyzed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). At high temperature of 1300 ℃, the molten CMAS permeated through the cracks and pores on barium silicate bulks. The macroscopic morphology indicated that the CMAS completely infiltered into the interior of the Er2SiO5 bulks in a short time, and no glassy CMAS was found on the surface, but the condensed glassy CMAS remained at the center of the Er2Si2O7 bulks. The molten CMAS reacted with barium silicate to form a columnar apatite phase Ca2Er8(SiO4)6O2. The molten CMAS had good wettability with Er2SiO5/Er2Si2O7, so Er2SiO5/Er2Si2O7 and molten CMAS had close contact and dissolved each other. Element Er and Si entered into molten CMAS, and the apatite phase Ca2Er8(SiO4)6O2 formed. After the Er2Si2O7 bulk was infiltered by CMAS, the formed apatite was relatively dense, which could effectively prevent the CMAS from continuing to infilter through the gaps of columnar crystal or the pores, and the infiltering rate of CMAS was significantly reduced, and the infiltering depth was smaller than that of Er2SiO5 at the same corroding time. Rare earth bait double silicate Er2Si2O7 can effectively prevent CMAS from infiltering and exhibit better CMAS corrosion resistance.