Abstract: Studying gene flow of transgenic wheat helps establish a corresponding strategy to prevent transgene escape and germplasm contamination between compatible wheat genotypes. An experiment was carried out using transgenic wheat with resistance to wheat yellow mosaic virus (WYMV) as pollen donor, and Yangmai 158 and dwarf male-sterile wheat as pollen receptors, and two plots of the transgenic wheat, different in size (100 and 400 m²) and laid out in parallel as pollen sources. Gene flow frequency was monitored at different intervals from the pollen source to investigate effects of size of the pollen source and competition between pollens on gene flow of the transgenic wheat. Results show that size of the pollen source did not significantly affect transgene flow frequency, but variety of the two pollen receptors did. The male-sterile dwarf wheat was found to be significantly higher in transgene flow frequency at distance intervals of 0 and 2 m from the pollen source. The gene flow frequency of transgenic wheat declined dramatically with increasing distance from the source and was reduced to 0 over the test distance of 5 m. All the findings indicate that pollen competition may be a major factor influencing transgene flow and isolation by distance is one of the most effective methods to control pollen-mediated gene flow in wheat.