  Using the Modules for Experiments in Stellar Astrophysics code, we
investigate the influences of irradiation on ultra-compact X-ray binary (UCXB)
evolution. Although the persistent UCXBs have short orbital periods which
result in high irradiation flux, the irradiation hardly affects the evolution
of persistent sources because the WDs in these binaries have large masses which
lead to very low irradiation depth. The irradiation has a significant effect on
the transient sources during outburst phase. At the beginning of the outburst,
high X-ray luminosity produces high radiation flux, which results in the
significant expansion of WD. Then, the irradiation triggers high mass-transfer
rates, which can last several days for the transient sources with WDs whose
masses are larger than $\sim0.015 M_\odot$ or several hundred years for these
sources with WDs whose masses are less than $\sim0.012 M_\odot$. The observed
three persistent UCXBs, XTE J0929-314, 4U 1916-05 and SWIFT J1756.9-2508, may
belong to the latter.
