The invention relates to the field of microbial fermentation, in particular to a preparation method of a compound Daqu, so as to solve the problems of the traditional Daqu such as single nutritional components of raw materials, longer starter-making and brewing time, low utilization rate of grains, high cost and the like. The preparation method comprises the following steps: (1) treating the raw materials of the Daqu; (2) inoculating aspergillus niger 41254, aspergillus niger UV-11, monascus, mucor racemosus, actinomucor elegans, rhizopus oryzae, saccharomyces cerevisiae, candida drusei, acetobacter, bacillus subtilis and lactobacillus delbrueckii 6100 into a conical flask containing the raw materials of the Daqu for culturing, then expanding the culture and obtaining a mother culture; and(3) adopting uncooked materials for making a starter, inoculating the obtained mother culture and the raw materials of the Daqu into a solid fermentation device, keeping the temperature at 30 DEG C-33 DEG C, continuing for 30-33h, discharging the starter and finally carrying out low-temperature vacuum drying. The preparation method enriches the nutritional components in the raw materials and improves the quality of a brewed product; and a plurality of bacterial strain are artificially added, thereby improving the utilization rate of the grains, shortening the starter-making cycle, improving the yield of the brewed product and reducing the production cost.