In this paper the pumping of a two level system by nearly resonant polychromatic field is discussed. It is pointed out that owing to the interference between field, one can obtain greater population inversion in the case of pumping by a monochromatic or dichromatic field. For the case in which the upper level splits into two nearby ones, the method of density matrix is used to calculate the steady-state solution for various parametric values. It is found that population inversion can be obtained at definite conditions.