The invention relates to a selective flocculation flotation method of micro-size fraction siderite and belongs to the technical field of mineral processing. According to the method, the micro-size fraction siderite is subjected to selective flocculation, specifically, a dispersant, namely citric acid, is added firstly to reduce heterogeneous condensation between the siderite and hematite as well as between the siderite and quartz, then a selective flocculant, namely alpha-starch, is added, flocculation of the micro-size fraction siderite and inhibition of the hematite are achieved, and flotation is conducted through an anionic collector, namely sodium oleate. According to the selective flocculation flotation method of the micro-size fraction siderite, the influence of the micro-size fraction siderite on reverse flotation of the hematite can be significantly reduced, the recovery rate of iron in iron concentrates is increased, the grade of the iron in the iron concentrates is improved,and important significance is achieved on effective utilization of iron ores containing carbonate.