A method of preparing a fermented seaweed used as an aquaculture feed is disclosed. The method includes providing Sargassum cristaefolium, and fermenting the Sargassum cristaefolium by Saccharomyces cerevisiae P13 at 26-30℃.一種醱酵馬尾藻製備方法,係包含:提供一重緣葉馬尾藻;及於26~30℃之溫度下,以一釀酒酵母菌P13醱酵該重緣馬尾藻;據此,可以製得作為水產養殖飼料之添加物的醱酵馬尾藻。