The characters and effects of sealand breeze in Yangjiang were studied. The ba sic data were taken from weather stations, automatic weather stations in Yangjia ng and two towers of 80metrehigh gradient observation on the seaside. The re sult shows that the western coast sea breeze formed earlier than the eastern coa st one. In surface layer, the sealand breeze increases with height. Sometimes in May, the sealand breeze is too weak to reach the height of 80m. The change from land breeze to sea breeze occurs mostly during 11:00-12:00. On th e contrary the change from sea breeze to land breeze happens at about 23:00, both dur ing the period of daily peak of pressure fluctuation. The sealand breeze can r each 70-75 km far from the coastline when it superimposes valley wind, but it ca nnot pass over the Mist Hill. During the period of sealand conversion, a conve rgent zone formed near the bay, which made the urban district of Yangjiang at it s northern side to be a rainy center from April to July. The sea breeze converse d in the pipe socket area near Yangchun and made this region become another rain y center. All above are important factors making Yangjiang to be the rainy cente r of Guangdong. In addition, if the sea-land breeze circulation was not broken down, Yangjiang coastal areas would not have high temperature weather.