Abstract: With large-scale extrapolation of commercial cultivation of genetically modified crops,biosafety issues caused by pollen flow from genetically modified plants have become a growing concern the world over. A two-year controlled field experiment was carried out at the transgenic crop environmental safety experiment base in Xuzhou,Jiangsu focusing on pollen flow from transgenic winter wheat N12-1 containing a NIb8 gene for resistance of wheat yellow mosaic virus (WYMV).The base was established and authorized by the National Biosafety Committee of China for growing transgenic wheat for environmental biosafety assessments. To study influence of wind direction on pollen flow from the transgenic wheat,the field experiment was laid out in concentric circles and wheat pollen density monitored in eight directions around the pollen donor at different intervals. Results show that pollen density of transgenic wheat declined dramatically with increasing distance from pollen sources in eight directions,however,the declining rate varied significantly with the direction,and was relatively lower in the lee. Meanwhile,to investigate effect of size of the pollen source on pollen flow,two tracts of pollen source,different in size（ 100 and 400 m²） were set up in parallel and wheat pollen density was monitored in the lee. Results show that a big size pollen source may have a lower pollen density declining rate within a given range,as compared to a small size one. All the findings indicate that wind direction,wind speed and distance from the pollen source are the major factors affecting pollen flow from the transgenic wheat.