For studying the evolution rules of the sea-land breeze, a statistical analysis of appearance and disappearance and evolution rules of PBL convergence line ass ociated with the sealand breeze along Bohai Gulf is done by using Tianjin wea ther radar CINRADSA and automatic meteorological station data. The corresponde nces between PBL convergence line and sealand breeze along Bohai Gulf are rese arched. The results show that: (1) The PBL convergence line forming along coastline is actually sealand breeze convergence line. (2) Sealand bre eze convergence line can be only monitored by radar from May to September each yea r, mainly in June to September. (3) On clear days, when a strong sealand breez e convergence line passes the radar or blows to the northwest of the radar, lan d breeze turns to sea breeze. (4) The stronger the intensity of sealand breeze convergence line and the higher sealand breeze convergence line stretches vert ically, the larger the speed of corresponding sea breeze.