Based on the statistical analysis of heavy precipitation in southeast coast of China in winter (December,January and February),the European Center winter precipitation data during 2011-2016 were classified by the EOF,REOF and North test methods,and the first and fourth REOF modes located inland were selected.The composite analysis of precipitation samples of the two modes shows that the composite precipitation centers are consistent with the multi-year statistical rainstorm centers in Fujian province.In combination with the heavy rainfall,there is an asymptotic convergence flow from north to south with a front zone at 1 000 hPa,which forms a synoptic scale asymptotic frontogenesis convergence line.The heavy precipitation is usually located on the left side of convergence axis where a cyclonic wind shear exists.This is a type of winter rainstorm system in southeast coast of China that has not been specifically concerned and discussed in the past.The structure of the rainstorm system is confirmed and diagnosed by an objective determination method and establishing a coordinate system of the system.In the cold and dry winter with less rain and prevailing northerly wind at the low level,this kind of system has both the thermal uplift in the front area and the dynamic uplift of convergence air flow,forming a vigorous ascending motion in the rain area.Meanwhile,through the orthogonal wind component of convergence line,the water vapor from adjacent sea surface is collected into the precipitation area,combined the southerly airflow at the west edge of the subtropical high at the middle and upper levels,forming a relatively deep confluence water vapor transport layer.By the non-adiabatic heating,the deep thermal convection instability is formed.Through the dry area wedging under the moisture mass,the wet dynamic instability of the lower dry and upper wet is formed,and the pseudo-equivalent potential temperature decreases with the increase of height,forming a convection instability layer of the upper warm wet and the lower cold dry.Therefore,the system has an important impact on the occurrence and development and the falling area of heavy rainfall in winter.The influence of environmental thermal mechanism is discussed by the simulations of WRF model.Results show that the condensation latent heat heating can affect the convergence position and intensity of the convergence line,the position and intensity of frontogenesis area,and then affect the activity of the system.The latent heat heating in the middle levels can prevent the advection sensible heat cooling into the warm air mass,and maintain the thermal instability and precipitation intensity in the rainfall area.The asymptotic frontogenesis convergence line is conducive to the occurrence of heavy rain in the large-scale precipitation in Fujian in winter,in which the condensation latent heat release plays an important role.