The steady thermal stress distributions and effect factors in a ceramic/FGM/metal composite EFBC plate considered constant material properties under convective heat transfer boundary were investigated by the FEM and the Sinpson method. From numerical calculation, when , T0=300K, Ta=400K and Tb=1 400K, the stress distributions in the plate were obtained. The results are as follows. With the increase of the FGM layer thickness, the stress distribution in the composite plate is more reasonable. Compared with M=0.2, when M=5, the compressive stress on the ceramic surface reduces by 10.2%, and the tensile stress on the metal surface reduces by 21.7%. With the increase of A, the variations of thermal stress curves become big. Compared with A=0, when A=3.99, the tensile stress on the metal surface increases by 198.0%, and the maximum compressive stress on the surface of ceramics increases by 66.0%. Compared with the mutation of thermal stress at the cohesive interface of ceramic / metal two-layered composite plate, the thermal stress of ceramic/FGM/metal composite plate is very gentle. Compared with , when , the maximum tensile stress on the metal surface increases 1.44 times, and the maximum compressive stress on the surface of ceramics increases 1.50 times. The results provide the foundations of theoretical calculation for the design and application of the composite plate.