Sea land breeze (SLB) is a common local mesoscale circulation in coastal areas, which varies local weather conditions and further affects the diffusion and transport of air pollutants. This study investigated the variation of meteorological conditions, air pollutants concentrations, and aerosol chemical composition under the influence of SLB circulation in a coastal city of Southeast China during Nov. 1 – Dec. 31, 2020, when SLB circulation frequently occurred. The day-night difference in meteorological parameters was amplified on SLB days with a marked daytime peak of T and UV while the nighttime pronounced minimum boundary layer height compared to non-SLB days. The average mass concentrations of NR-PM1 (non-refractory submicron particles) measured by a Q-ACSM were 9.6 ± 6.5 μg m^-3 on SLB days and 11.6 ± 7.3 μg m^-3 on non-SLB days, but the NR-PM1, as well as gaseous pollutants like NO₂ on SLB days, showed a marked peak in the late evening. The NR-PM1 on SLB days was characterized by a high fraction of organic aerosol (OA). Moreover, the NR-PM1 showed a significant increase of more-oxidized OOA (MO-OOA) during the sea breeze period, which was associated with enhanced photochemical reactions due to strong UV and elevated O_x. Comparison between a SLB case and a local pollution case further highlighted the elevated contribution of OOA to NR-PM1 and the cyclic amplification of air pollutants in SLB conditions. Our study enhances the understanding of the influence of SLB on air pollutants and aerosol chemical composition and provide a plausible explanation for the atmospheric pollution processes in coastal cities.