Based on Doppler weather radar data,conventional observation data and automatic station data ,a warm-sector heavy rainfall process in Ya'an city on July 14, 2018 was analyzed from the environmental conditions and the developing communication mechanisms of radar echoes.The results indicate that:①The initial echoes the development and maintenance of the echoes are mainly due to the influx of upstream convective system and the re-triggering mechanism in convective system;②When the trend of echo is consistent with the mean wind, it can be judged that the echo will develop and spread along the mean wind in the future. ③The formation of cold pool can be judged by analyzing the changes of air pressure and temperature of surface meteorological elements. The sudden rise of air pressure and drop of air temperature indicate that the cold pool has been formed, and the time period when the two trends overlap indicates that the cold pool continues to appear. At this time, if the warm and wet air flow is continuously conveyed in the low-level wind field of radar, it is beneficial to trigger new convective units in the convective system, and the re-triggering mechanism in the convective system is conducive to the long-term maintenance of strong echoes.