  The particle identification of charged hadrons, especially for the separation
of $K$ and $\pi$, is crucial for the flavour physics study. Ionization
measurement with the cluster counting technique, which has much less
fluctuation than traditional $dE/dx$ measurement, is expected to provide better
particle identification for the BESIII experiment. Simulation studies,
including a Garfield++ based waveform analysis and a performance study of K/\pi
identification in the BESIII, offline software system have been performed. The
results show that $K/\pi$ separation power and PID efficiency would be improved
significantly in the momentum range above 1.2 GeV/c using cluster counting
technique even with conservative resolution assumption.
