The present application provides a biodegradable magnesium alloy without rare earth elements. The magnesium alloy comprises the following elements in percentage by mass: Zn 1.0-5.0%; Mn 0.1-1.0%; Ca 0.1-1.0%; Sr 0.1-1.0%; Sn 0.1-3.0%; Zr 0.1-0.8%; and Mg balance. The impurity in the magnesium alloy does not contain rare earth elements. The present application also provides a method for preparing the above biodegradable magnesium alloy and use in the preparation of medical devices. In the present application, Mg is used as the main components and mixed with a specific proportion of Zn, Ca and Mn to prepare the alloy. The biodegradable magnesium alloy of the present application has a controllable degradation rate and strong mechanical strength, and there are no harmful elements to a human body, and the degradation of the alloy in the human body will not affect human body.