Abstract: In order to study the difference between rotate speed and blade incidence adjustment of contra-rotating auxiliary fan, numerical simulation are carried out at different working conditions by using Fluent. And simulation models are verified by experiment. Pressure, volume, efficiency and shaft power at different pipe distance are analyzed. Results show, both ways can change fan’s output ability, but they have different essence, efficiency decreases as blade incidence reduces, while doesn’t change by speed; combing two means of adjustment can realize high efficiency and energy saving operation.