The invention relates to a preparation method for a superparamagnetism ferroferric oxide sub-micron hollow microsphere. The preparation method comprises the following steps: 1) taking a reducing agent, an iron source and an alkali source, and dissolving into distilled water; 2) dissolving a surfactant into a solution obtained from step 1); 3) introducing a solution obtained from step 2) into a reaction kettle, reacting in a drying oven, performing natural cooling to room temperature for seasoning, water washing, alcohol washing, and drying in a vacuum drying box, so that the superparamagnetism ferroferric oxide sub-micron hollow microsphere is obtained. The preparation method has the following good effects: 1) according to the invention, the ferroferric oxide sub-micron hollow microsphere is compounded, and has superparamagnetism, high saturation magnetization and excellent oxidation resistance; 2) dispersing agents such as PEG (polyethylene glycol) and PVP (polyvinylpyrrolidone) are adopted to solve the problem of magnetic microsphere agglomeration, so that the ferroferric oxide sub-micron hollow microsphere with uniform particle size is obtained; 3) according to the invention, adopted raw materials is cheap, so that cost is minimized.