The low alloyed bainite ductile iron is obtained by alloying and austempering in room-temperature machine oil. The microstructure is investigated. The mechanical properties are discussed. In general, the number of white-bright zones and segregation is increasing with the increasing in the content of Mn, but the impact toughness is decreased. Therefore, the content of Mn is no more than 0.5 wt.%. The microstructure of bainite, martensite and a little retained austenite in the matrix of the ductile iron was investigated by scanning electron microscope (SEM). The hardness and impact toughness of the ductile iron subjected to heat-treatment are 54~56 HRC and 14.2 J/cm2, respectively. The substitution of 0.3~0.5wt.% Mo by 0.7~1.0 wt.% Mn can be realized in the bainite ductile iron.