  We investigate the pseudospin-dependent density-energy relation (whose
differential with respect to energy is density of states) of a monolayer
graphene under intense terahertz laser field by exactly solving the
time-dependent Schr\"{o}dinger equation with help of Floquet's theorem. We find
that psedospin polarization can be induced by a circular polarized terahertz
laser field. The psedospin polarization in K and K$^{\prime}$ valleys can be
exactly opposite sign when the electron densities in these two calleys are
equivalent. Further more, we find that the psedospin polarization can be
manipulated by the strength, frequency, and especially the polarization
orientation of the field.
