Abstract: Sea-land breeze is one of the main triggers of convective weather during spring and summer in Hainan Island. To better understand the relationship between sea-land breeze and lightning activities over Hainan Island, and therefore to improve the prediction capability of lightning activities over Hainan Island, based on the lightning data from Lightning Location Monitoring Network and hourly surface wind direction and wind speed data from mesoscale automatic weather stations of Hainan Meteorological Service, the relationship of temporal and spatial characteristics of lightning activities over Hainan Island and sealand breeze was studied using statistical method. Result shows that the lightning mainly occurs in spring and summer over Hainan Island. In most areas, lightning occurs during the daytime, especially during the afternoon. On the southern and western coasts, lightning is more active during the nighttime than the daytime. Result also indicates that, in spring and summer, the active sea-land breeze has a key impact of lightning activity and is likely one of the important reasons led to the temporal and spatial distribution characteristics of lightning activities over Hainan Island. Over the northwest inland and the northeast coastal areas, the northerly sea-breeze converges with the southerly environmental wind during the daytime, resulting in more lightning activities during the daytime. Over the southern coastal areas, lightning is more active during the middle of the night and the morning due to the convergence of the northerly land-breeze and the southerly environmental wind.