Our study reveals that the magneto-electronic properties of the zigzag nanographene ribbons are tuned by the external electric fields. The spatially modulated electric field ( the uniform transverse electric field) converts the dispersionless Landau levels into subbands with the sinusoidal ( linear) energy dispersions. The energies of the band-edge states are affected by the electric potentials. The localization positions and the spatial symmetry of the Landau wave functions are altered. The modulated electric potential with shorter periodic length has stronger influence on the quasi-Landau levels. The magneto-optical absorption spectra are expected to be changed by the external electric fields. (C) 2010 Elsevier B.V. All rights reserved.