The invention discloses a preparation method of high-content salvianic acid A sodium. The preparation method is characterized in that hot acid water extraction is performed on salviae miltiorrhizae, and a salt formation method by heating sodium hydroxide is used coordinately. The preparation method has the advantages that problems that many impurities exist, salvianic acid A is severely damaged, transfer rate is low, many purifying procedures are needed, the process is complex, the period is long, impurity removing is not thorough, the finished-product extract is low in salvianic acid A sodium content, and stability is poor caused by high-temperature decoction reflux extraction and high-temperature concentration are avoided effectively; oxidized and degraded salvianic acid A during extraction can be reduced, the salvianic acid A transfer rate in extract and salvianic acid A sodium stability are increased, the salvianic acid A is prevented from being destroyed by high temperature, no antioxidant is added, the storage stability of the salvianic acid A sodium is guaranteed in an acid environment, and the method is easy in operation implementation and suitable for large-scale industrial production.