The invention relates to a preparation method of high-concentration malt wort, which comprises the following steps of: boiling the filtered malt wort in a boiler; adding syrup for beer prepared from starch by specific processes and hydrolysis of multiple enzyme preparations in a mash boiler in advance before the boiling process is finished; and then, depositing by rotating and cooling the hot malt wort mixed by the boiler to obtain the high-concentration malt wort. The malt wort of the invention has short preparation period and short conversion time, thereby greatly improving the efficiency for converting starch into syrup. In addition, specific starch decomposition processes are adopted by the invention, the step of secondary liquefaction is increased, and the syrup converted by the compounding technology of three kinds of amylolytic enzyme preparations meets the requirements of beer brewing, thus a brewery can save the transportation cost of syrup purchase and a large amount of energy consumption in the processes of preparation and concentration of bought-in syrup. Meanwhile, the syrup for beer brewing, which is prepared from starch, is directly added into the boiler and does not need to participate in the whole process of boiling malt wort, thereby reducing the production cost of beer malt wort, and saving the energy consumption.