The invention relates to a preparing method of a zinc magnesium function gradient biological composite. Magnesium powder, zinc powder and HA powder are adopted to serve as raw materials, ball milling powder mixing, die filling and vacuum discharge plasma sintering are carried out, and a zinc magnesium composite of two gradient structures is prepared. The preparing method is advanced in technology, data are full and accurate, a prepared zinc magnesium gradient material is high in combination strength on the interface, the debinding phenomenon is avoided, wear resistance and mechanical properties(the crush resistance strength is 293.66MPa, the elasticity modulus is 8.0 GPa, and breaking tenacity is 9.327 MPa.mm<1/2>) of all gradient layers are matched with the natural bone, the stress shielding effect is effectively avoided, and the preparing method is an ideal preparing method for a degradable biomedical metal gradient material.