In order to determine the installation parameters of mixing fans in open dairy cow house, field experiment was conducted to measure airflows in dairy cow house in Tianjin. After establishing 16 geometric model with different installation parameters of mixing fans，3-D steady simulation of airflow distributions was carried out in cow house. The effect of air flow disturbances was analyzed with fans installation height and tilt angle as influence factors and the ratio of the area where air velocity more than 1.0 m/s to total region in two surfaces which above the ground 1.0 m and 1.5 m as evaluation indexes. The result showed that there was no significant difference on effect of air flow disturbance between different installation height（P＞0.05）in the same tilt angle. The optimal tilt angles of fans were that fans over the cow bed of 20° and fans over the head gate assembly of 10°.