  Hawking radiation can usefully be viewed as a semi-classical tunnelling
process that originates at the black hole horizon. For the stationary
axisymmetric BTZ black hole, a generalized Painleve coordinate system
(Painleve-BTZ coordinates) is introduced, and Hawking radiation as tunnelling
under the effect of self-gravitation is investigated. The corrected radiation
is obtained which is not precise thermal spectrum. The result is consistent
with the underlying unitary theory. Moreover, Bekenstein-Hawking entropy of BTZ
black hole is not necessarily corrected when we choose appropriate coordinate
system to study the tunnelling effect.
