Abstract: In order to comprehensively evaluate the mixing effect and drag loss of static mixers in selective catalytic reduction (SCR) system, a comprehensive performance evaluation index combined the uniformity of flow field and drag characteristics-dimensionless mixing efficiency η was proposed. According to the field requirements, the comprehensive performance of the system was evaluated by numerical simulation method with circular, petal and SMV mixers as examples. Results show that the η of circular mixer, SMV mixer and petal-shaped mixer are 16.18%, 22.50% and 26.88%, respectively. The petal-shaped mixer has the best comprehensive performance. Under the condition of sequence arrangement, same direction layout and coverage rate of 37%, the overall performance of the petal-shaped mixer is the best, and its dimensionless mixing efficiency η is 28.60%, which is 6.40% higher than before optimization.