【Background】As a simple and effective tool, Gaussian plume model is commonly used to calculate the pollen dispersal concentration and determinate the gene flow safety distance. In order to simulate the pollen dispersal concentration of genetically modified crops, the accurate estimation of source strength contribution is essential in Gaussian plume model. 【Method】In this paper, using mathematical derivation, we propose for the first time a method how to divide equally circular pollen source area into lots of smaller parts and identify the center point coordinates of each parts. An example of its application example is given. 【Result】Based on observed data from the maize pollen dispersal and gene flow experiment conducted in Gongzhuling (Jilin Province, northeast China), the formula was applied into Gaussian plume diffusion model to calculate the contribution of each small parts′ pollen source strengths. The maize pollen dispersal concentration at different distances out of the pollen source area was estimated. The simulated and observed values results from these calculations showing a similar values suggest that good agreements, and it showed that the application of the formula to simulate pollen dispersal could obtain satisfactory results and could be appropriate. 【Conclusion and significance】The formula to determine the center point coordinate of each small pollen source area is reliable. This method is useful to improve the convenient calculation of each small source strength contribution to pollen concentration outside of source area with Gaussian plume model.