The invention provides a processing method of dark brown sugar, and the method comprises the following steps of: S1, peeling sugarcane, cutting sugarcane into sections, performing juicing, filtering juice, adding sucrase and maltase, adjusting conditions for enzymolysis, deactivating enzyme, and conducting filtering and concentrating to obtain concentrated sugarcane juice; S2, boiling the concentrated sugarcane juice at 150-190DEG C for 30-50min, adding brown granulated sugar, performing stirring and dissolving, conducting boiling at 190-220DEG C for 60-100min, adding stevioside, performing stirring and dissolving, and conducting boiling at 220-270DEG C for 30-60min; and S3, spreading the boiled liquid on a cold bed, neatly scribing the liquid by using a scribing tool, and packaging and selling the liquid after the liquid is completely cooled and formed. According to the method, industrial continuous production can be achieved, the problem that traditional dark brown sugar production is complex in manual operation is solved, no chemical reagent or food additive is added in the processing process, and the green safety of food is guaranteed.