Holographic Entropy Bound of a Nonstationary Black Hole

In accordance with the holographic principle, by counting the states of the scalar field just at the event horizon of the Vaidya--Bonner black hole, the holographic entropy bound of the black hole is calculated and the Bekenstein--Hawking formula is obtained. With the generalized uncertainty principle, the divergence of state density at event horizon in the ordinary quantum field theory is removed．With the residue theorem, the integral trouble in the calculation is overcome. The present result is quantitatively tenable and the holographic principle is realized by applying the quantum field theory to the black hole entropy problem. Compared with some previous works, it is suggested that the quantum states contributing to black hole entropy should be restricted on the event horizon.