The invention discloses a preparation method of an aluminum-silicon alloy for electronic packaging. The preparation method comprises the following steps of S1, jetting and deposition for blank making;S2, homogenizing treatment; S3, densifying treatment; S4, isothermal rolling; and S5, annealing treatment. According to the preparation method, the aluminum-silicon alloy of the final thickness or approaching the final thickness is directly made by combining quick solidification with a traditional plastic deformation means, so that mechanical machining procedures such as line cutting, saw cuttingand milling are omitted, the material utilization rate and the production efficiency are greatly improved, and the preparation method is suitable for industrial production; and the aluminum-silicon alloy obtained with adoption of the method has excellent mechanical machining, surface plating and welding properties, meets the using requirements of electronic packaging and is suitable for electronic packaging cover plate materials.