In order to research the drift mechanism and develop effective anti-drift technology, phase Doppler particle analyzer (PDPA) was used to analyze droplets size and velocity distribution in spraying fan near flat fan nozzles. Results showed that the distribution of droplets size (VMD) in spraying fan sectional view was like a concave, and droplets size varied following quadratic polynomial in cross-symmetry plane and lengthwise-symmetry plane of spraying fan. Droplets drifting easily were located in the 300~500mm of the centre of spraying fan far from nozzles. Entrained air velocity in spraying fan varied following Gauss distribution, and the flow field of entrained air was similar to a submerged air jet. Major drifting areas were evaluated depending on the droplets size and velocity distribution in spraying fan. Results showed that there were three major drifting areas in spraying fan: cross edges of spraying fan, wake region of spraying fan and outer layer facing wind of spraying fan.