Perovskite-type BiMnO3, in which ferroelectricity and ferromagnetism co-exist,has potential applications in sensor and information storage. Usually, BiMnO3 is synthesized under high temperature and high pressure in a gold capsule,which restricts its application and development extremely. In this paper, we synthesize the BiMnO3 nanopowders with MnCl2·4H2O,Bi2O3, NaOH,HNO3 and polyglycol at 100 ℃ by the co-precipitation method successfully, in which the conditions of temperature and pressure are reduced, thereby economizing the energy sources and lowering the cost. Their microstructure and magnetic properties are measured by using X-ray diffraction (XRD), transmission electron microscope(TEM) and vibration sample magnetometer(VSM). The effects of synthetical condition and the calcined temperature are also discussed.