There are uncertainties in calculating atmospheric diffusion parameters on assessments of the environment. Footprint analysis method is used to confirm the horizontal diffusion scale and time,and finally calculate the horizontal diffusion parameters by using the data measured by the threedimensional sonic anemometers on the coast of Balong，Guangxi Province. The results show that：1) diffusion scale and time have obvious influences on determination of diffusion parameters. 2) The diffusion parameters of the land breeze are larger than that of the sea breeze, which implies that land breeze is in favor of pollution diffusion. 3) The diffusion parameters are conservative and depend on local topography and regional characteristics. Footprint analysis method may be helpful in obtaining diffusion parameters.