HUANG, CG (reprint author), ACAD SINICA,INST HIGH ENERGY PHYS,BEIJING 100039,PEOPLES R CHINA.
It is shown in this paper that there is a difficulty in conventional black hole thermodynamics. To overcome the difficulty we introduce a "surface" near the event horizon as an additional thermodynamical object. The mass and entropy of the additional "surface" are the same as the correction of mass of Schwarzschild black hole obtained in the back-reaction program up to a constant factor. This implies that some effects of back reaction are automatically considered in our thermodynamic phenomenological treatment.