A novel linear polyurethaneurea emulsion was synthesized from poly(propylene oxide) diol, toluene diisocyanate, dimethylol propionic acid, 2-methyl-1,3-propane diol and ethylenediamine. The effect of the fraction of and the distribution of ionic group on the properties of polyurethaneurea emulsion was investigated by infrared spectroscopy (i.r.), differential scanning calorimetry (d.s.c.), transmission electron microscopy (TEM), a rotary viscometer, etc. In polyurethaneurea investigated, hydrogen-bonds existed not only in the hard segment but also in the soft segment. With increasing the fraction of ionic groups, microphase separation was enhanced and the polyurethaneurea emulsion viscosity increased. In addition, the synthetic method has a profound effect on the distribution of ionic groups, and the emulsion having well-distributed ionic groups is more stable in storage.