  We have discussed the search of the genuine CP violation in a neutrino
factory, in which well known neutrino beams are provided by a high intensity
muon storage ring. Both $\Delta P(\n_\a \Ar \n_\b)$ and CP odd asymmetry
$A_{CP}$ in neutrino oscillations are investigated by taking account of the
atmospheric neutrino data and the solar neutrino data. If the large mixing
angle MSW solution is taken, the magnitude of $\Delta P(\n_e \Ar \n_\m)$ could
be 1%. If $s_{13}$ is lower than 0.05 with the maximal CP violating phase, the
matter effect is negligible in $\Delta P(\n_e \Ar \n_\m)$ and $A_{CP}$. We have
proposed how to extract the genuine CP violation effect in the three family
scheme from the neutrino oscillation data $\Delta P(\n_e \Ar \n_\m)$, $\Delta
P(\n_\m \Ar \n_e)$ and $\Delta P(\n_e \Ar \n_\tau)$.
