The statistical characteristics of thunderstorm and gale over western Bohai Sea were analyzed using dense observation data of seven stations at islands， platforms and buoy stations in western Bohai Sea from May to September during 2011-2016. The results showed that the thunderstorm and gale forces in western Bohai Sea are mainly the maganitude of 8-9, which are seen in the more southern part of the western Bohai Sea， mostly in June， then in July and rarely in May. The process in June, mostly occuring from 19:00 BT to 23:00 BT, is related to cold vortex twice as many as highlevel trough, and the most is related to band echo， which accounts for 68.8%. The sea surface temperature is 6℃ per longitude lower than the coastal temperature in 6-12 h before the occurrence of 〖JP2〗thunderstorm and gale, but the sea surface temperature and pressure are higher 4℃ per longitude and lower 2 hPa per longitude than in coastal area in 1-2 h before thunderstorm and gale. At the same time， the index thresholds of thunderstorm and gale were analyzed using corrected sounding datas. The results showed that BCAPE，LI，WINDEX and the 0-3 km vertical wind shear are more obvious in western Bohai Sea than in North China. The convection index thresholds of BCAPE， LI， WINDEX and 0-3 km vertical wind shear which could offer references for the forecast of thunderstorm and gale in western Bohai Sea from June to September are given, under background of highlevel trough and cold vortex.