Statistical entropy of Reissner-Nordstrom black hole

By using the method of quantum statistics, we directly derive the partition function of bosonic and fermionic field in Reissner-Nordstrom black hole. It is the same as the one obtained by solving wave equation approximately. Then via the improved brick-wall method, membrane model, obtain that the en tropy of bosonic and fermionic field in black hole is proportional to the a rea of horizon. In our result, the stripped term and the divergent logarith mic term don't exist any more. The problem that the state density is diverg ent around the horizon doesn't exist either. We also give the influence fac tor of the spining degeneracy of various particles on the entropy of black hole. In the whole process, we do not take any approximation. We offer a ne w simple and direct way of calculating the entropy of different complicated black holes. (C) 2001 Elsevier Science B.V. All rights reserved.