Based on the conventional meteorological data, physical quantity data, hourly PM2.5 concentration data and laser radar data, two distinct temporal and spatial distribution characteristics and diffusion condition of pollution under the control of sustained easterly system in Shanghai are comparatively analyzed. The results show that landsea temperature difference obviously affects the vertical transportation of pollutants. In the 26 January process, the sea surface temperature is higher and easterly flow is warm advection relative to the interior. Landsea thermal contrast makes the vertical temperature stratification in the surface layer tend to 〖JP2〗be unstable and speed up the vertical diffusion of pollutants in the boundary layer. On the contrary, In the 10 March process, the sea temperature is lower and easterly flow is cold advection relative to the interior. Landsea thermal contrast makes the vertical temperature stratification in the surface layer tend to be stable and inhibit the vertical diffusion of pollutants in the boundary layer. In addition, the laser radar data can intuitively reflect the vertical distribution of pollutants and have a certain guiding significance for our understanding of transmission characteristics and formation of pollution process.