The invention belongs to the field of the search of multiferroic materials, and particularly discloses a pure-phase bismuth ferrite powder body and a preparation method thereof. In the method, firstly, a self-assembling hybrid system is utilized for preparing hydrothermal precursor reaction liquid, then, PEG-2000 is added, and finally, crystallization is carried out under a hydrothermal condition to obtain a product. The bismuth ferrite powder body prepared with the method has a controllable micrometer-nanometer composite structure and also has an obvious lattice orientation. Meanwhile, the prepared product is high in purity, does not contain other impurities, is simple to prepare, is lowcost and is very suitable for mass production.