Abstract: Exploring the cause of strong convective weather in Zhejiang will improve meteorological service for agricultural production. In this paper, the conventional observation data, NCEP reanalysis data and Doppler weather radar data were used to analyze widespread gale and a hail weather process occurred in Zhejiang on August 17, 2017. The results showed that: (1) the strong convection weather process generated under the condition of weak convection, with the eastward and southwest airflow of the high groove increasing, the dynamic conditions, thermal conditions and water vapor conditions were improved, and the unstable stratification was strengthened, local geothermal convection, low-level shear and ground convergence were the trigger condition; (2) vertically integrated water content density was an important radar indicator of the hail, in addition, the hail probability was very high when the local VIL/ET≥3.9 in Zhejiang; (3) the rapid drop of the echo centroid of thunderstorm indicated the occurrence of the gale weather, the dry inflow jet behind the thunderstorm was conducive to the development of the system and the formation of squall lines, long-time maintenance of large stratiform precipitation echoes after the decrease of thunderstorm was the main cause of heavy rainfall; (4) there were two main stages of gale weather, one was caused by the eastward movement of squall line and the other was the increase of single storm after squall line weakening, the weak mesocyclone inside the squall line was one of the main causes of the gale along the Hangzhou Bay coast, the increase of storms into the sea might be caused by the difference of thermal properties between sea and land.