Abstract: Two coastal heavy rains on August 4-5 and 21-22, 2010 were caused by subtropical high. Based on the conventional observation data, precipitation data from automatic stations and NCEP reanalysis data from NCEP/NCAR center, it is diagnosed mainly from circulation situation, influence system, physic and numerical forecast products, providing a basis for coastal zone in Hebei heavy rains. The results indicate: both of the two processes, which happened against a favorable circulation background had the characteristics of the coastal zone in Hebei summer rainstorm, are typical of the subtropical high edge heavy storm. The rainstorm area which corresponded well with the convergence zone of vapor flux water vapor near the boundary layer has a growth effect on the precipitation. Differences appeared from the trigger mechanism and the stability of convection when it has big-heavy rains in Qinhuangdao according to T639 forecast production. If there is a trigger mechanism of mesoscale system in such area, it will probably be the falling area of coastal heavy rains.