Abstract: The paper aims to study the characteristics of a heavy rainfall on the west pacific subtropical high edge in summer, and improve the heavy rainfall forecasting models and factors and promote the prediction accuracy. Using the data of micaps, upper and lower wind field and T639L60 variable, the circulation situation, upper-lower jet, vertical speed, relative humidity of a heavy rainfall during August 4-5, 2010 in the west coast of Bohai were analyzed. The results indicated that: subtropical high, westerly trough and low level shear line, surface cyclone formed the major effect system of this heavy rainfall, the intersection of high altitude cold air and low warm wet air at west coast of Bohai touched off the heavy rainfall; low level convergence and high level divergence offered dynamic conditions, low level southwesterly jet and surface continuous easterly winds offered abundant moisture; this heavy rainfall occurred between 584 dagpm and 588 dagpm contour line of subtropical high where low level shear line existed, right side of 200 hPa high level jet and left side of 850 hPa low level jet; enhancing of high level jet, developing of instable convection stratification, enhancing of atmospheric lifting movement, invading of high level cold dry air, importing of low level warm wet air indicated heavy rainfall; weakening of high and low level jet, disappearing of low level warm wet air, invading of low level cold dry air indicated precipitation disappearing.