The spectral width of transverse magnetic (TM) lasing modes in two-dimensional random media is theoretically investigated by using the time-dependent theory. The evolution curve of the spectral width of TM-polarization modes versus the pump intensity is obtained from which one can calculate some characteristic parameters of the emission, e.g. the threshold. The results show that, from the view of spectral width, the emission of the TM-polarization lasing modes have better out-put property than that obtained previously with TE-polarization.