Abstract: The main useful mineral in a magnesite ore liaoning province was magnesite, the main gangue minerals were dolomite, pencil stone, quartz and so on.The content of MgO was 97.71% the content of the main impurity SiO₂ 3.19%.The indexs of experiment of contents of SiO₂0.28%, content of MgO 97.71% in concentrate,rate of concentrate being 71.820% on the condition of fitting griding fineness being 72% and medicament by using the reverse flotation and flotation flowsheet.