The invention relates to high-strength high-ductility biodegradable Zn-Mn-Mg series zinc alloy and a preparation method. The alloy is prepared from the 0.02 to 0.49% of Mn and 0.001 to 0.3% of Mg, wherein Mn is a main alloying element, Mg is a secondary alloying element, and the Mn content is not lower than the Mg content in the alloy; at least one of Na, K, Ca, Sr, Ti, Fe, Cu and Ag elements is selected, the total content of the alloying elements added to the Zn-Mn-Mg series zinc alloy does not exceed 2%, and the balance is Zn. The basic preparation process of the zinc alloy comprises the steps of vacuum directional solidification and extrusion; on the basis of the steps, at least one of the following processing methods can be selected for processing again: two-stage heat treatment, extrusion, rolling, drawing and annealing. According to the preparation process, the processing plasticity of the zinc alloy can be given to the maximum, and multiphase multiscale directional tissues can be obtained, so that the alloy has excellent overall performance. The tensile mechanical properties of the zinc alloy at room temperature include the yield strength of 260 to 430 MPa, the tensile strength of 305 to 580 MPa and the elongation of 18.5 to 55%, and the zinc alloy is suitable for medical implants and is especially suitable for biodegradable stents.