The large-double-blade impeller has a broad application prospects in rapid reactions of viscous systems. In syrup aqueous solution with viscosity of 0.8 Pa s, the influence of feeding location on the micromixing performance of the novel large-double-blade impeller was studied experimentally by adopting the iodide–iodate reaction system, and the distribution of energy dissipation rate in the stirring vessel was obtained by numerical simulation method for the micromixing based on standard E model and eddy-dissipation-concept (EDC) model. The results of simulation agreed well with the experimental data, both of which showed that the feeding location has an important effect on the micromixing performance. Feeding in the blade area is more favorable to reducing by-products and improving micromixing quality than in other areas under the same conditions for its comparatively large local energy dissipation rate. These results provide useful guidelines for the optimal design and operation of the novel large-double-blade impeller in rapid reactions of viscous system.