Abstract: There is a problem of large measurement error in the front fan drift multi-point measurement method of the air quantity of the main fan currently in use. To solve this problem, the simulation model for three common fan drifts is established, and the variation law of airflow distribution caused by the installation of the wind sensor is analyzed. According to the cloud map of longitudinal velocity distribution in the fan drift, the airflow distribution at the section of the sensor mounting bracket changes dramatically due to the interference of the bracket. After 200 mm of the leading bracket section, the wind velocity distribution tends to be uniform and the influence of the bracket on the airflow is reduced. The influence is minimal at the leading bracket of 250 mm, which can be used as the reference position for the sensor probe installation. Taking the square fan drift as an example, the experimental verification is carried out. The results show that: the measurement error is the greatest when the sensors are installed at the cross-section of the bracket at the selected 8 working points. With the distance increase of the sensor is mounted forward, the measurement error decreases gradually and reaches the minimum at 250 mm.