The invention relates to a large mode field ytterbium-doped active optical fiber which is characterized in that the large mode field ytterbium-doped active optical fiber is composed of a first core layer, a second core layer, a first inner wrapping layer, a second inner wrapping layer, an outer wrapping layer and a protection layer which are arranged from inside to outside in turn. The invention also relates to a preparation method of the large mode field ytterbium-doped active optical fiber. The large mode field ytterbium-doped active optical fiber has the advantages of large mode field areaand can acquire high beam quality through the bending die selection method.