The invention discloses a soybean paste brewing process which comprises the following steps: (1) dividing soybeans into two parts, namely soybeans 1 and soybeans 2; (2) cooking soybeans 1, crushing, cooling, inoculating yeast seed for starter propagation, adding salt and a small amount of water, and performing sun-curing fermentation to obtain a semi-finished product of soy sauce mash 1; (3) steaming and cooking soybeans 2, cooling, adding flour, uniformly mixing, inoculating yeast seed for starter propagation, adding saline water, and carrying out sun-curing fermentation to obtain a semi-finished product of soy sauce mash 2; (4) uniformly mixing the semi-finished soy sauce mash 1 and the semi-finished soy sauce mash 2 with saline water, and fermenting to obtain soy sauce mash 3; and (5) adding a flavoring agent into the soy sauce mash 3 for blending, boiling for 10-40 minutes, sterilizing, cooling and filling to obtain the soybean paste. According to the brewing process, the quality, enzyme activity and decomposition degree of finished koji are improved, the fermentation time is short, and the utilization rate of raw materials is high; compared with the traditional technology, the physicochemical indexes of the obtained soybean paste blank are obviously improved, and the soybean paste is red and strong in color, rich in fragrance and prominent in delicate flavor and mellow taste.