The entropy calculated via brick-wall method comes from a thin film near the event horizon

The brick-wall method put forward by 't Hooft has contributed a great deal to the understanding and calculating of the entropy of a black hole. Howeve r, there are some drawbacks in it such as little mass approximation, neglec ting logarithm terms, and taking the term including L-3 as a contribution o f the vacuum surrounding the black hole. Moreover, the fundamental problem is why the entropy of scalar field or Dirac field surrounding a black hole is the entropy of the black hole itself. It is well known that the event ho rizon is the characteristic of a black hole. The entropy calculation of a b lack hole should be only related to its horizon. Due to this analysis, we i mprove the brick-wall model by taking that the entropy of a black hole is o nly contributed by a thin film near tile event horizon. This improvement no t only gives us a satisfied result, but also avoids the drawbacks in the or iginal brick-wall method. It is found that there is an intrinsic relation b etween the event horizon and the entropy. We also calculate the entropy of Schwarzschild-de Sitter space-time via the improved method, which can hardl y be resolved via the original model.