Abstract: In this paper a new simplified form of Biot's general solution for the steady thermoelastic plates is given first. It looks like the famous Papkovich-Neuber's general solution of isotropic elastic mechanics. Generalized from problems of isotropic elastic plates, the problems of thermoelastic plates are focused A new refined plate theory is derived by using Lur'e operator from the Biot's general solution given above without any prior hypothesis. In the meantime, the proof that the Biot's general solution does not lose any generality is given.