  We discuss in this paper The experimental results on maximum psedo-rapidity
$\eta_{max}$ distribution in the charge exchange process $e+p\to e+n+X$ in ZEUS
Collaboration at HERA. We calculate the contributions of \regg ($\rho$-Reggeon
associated with $\rho$ meson) from regge phenomenology and $\pi^{+}$-exchange
from pion cloud model. The results show that neither the \regg-exchange nor the
pion cloud model alone can explain the experimental data well, but after
considering both these two processes together, by using Monte Carlo simulation,
a good agreement between theoretical results and experimental data is found.
This means that in discussing the large rapidity gap phenomena in deep
inelastic scattering, both of the two processes play substantial role.
