  We study a two-dimensional electron system in the presence of both Rashba and
Dresselhaus spin-orbit interactions in a perpendicular magnetic field. Defining
two suitable boson operators and using the unitary transformations we are able
to obtain the exact Landau levels in the range of all the parameters. When the
strengths of the Rashba and Dresselhaus spin-orbit interactions are equal, a
new analytical solution for the vanishing Zeeman energy is found, where the
orbital and spin wave functions of electron are separated. It is also shown
that in this case the Zeeman and spin-orbit splittings are independent of the
Landau level index $n$. Due to the Zeeman energy, new crossing between the
eigenstates $|n, k, s=1, \sigma>$ and $|n+1, k, s^\prime =-1, \sigma^\prime>$
is produced at certain magnetic field for larger Rashba spin-orbit coupling.
This degeneracy leads to a resonant spin Hall conductance if it happens at the
Fermi level.
