A mesoscale observational analysis is performed of an event of rainstorm and intense convective weather as a robust happening during a 100-yr return period on August 10, 2006 in the Song-Nen Plain of NE China by use of minute-level automatic-station data, high-resolution satellite cloud maps, new-generation Doppler soundings and conventional observations. Results show that this event of rainstorm and robust convective weather is bound up with the genesis and development of a squall line, which causes great change in station meteorological elements on its way. At the Tailai station, for instance, precipitation is the strongest, reaching 90.8 mm/h, where temperature drops by 21.5°C, pressure rises by 4.7 hPa and winds peak between 13.3 to 22.6 m/s during the squall passage. The squall line is displayed as an elliptical MCC on satellite cloud maps and in its mature stage as a squall line on radar soundings. This squall shows a comma-form meso -β convective storm before its genesis, followed by propagation towards the southwest part of the storm and showing its bow-like echo zones followed by gradual appearance of multiple super cells, viz., multi-cell storm in the southwestern end of the echoes. These intense convective storm comprise linear strong convective echo bands, ~315 km in total length and 50 km wide, persisting for 7 hrs. When the squall line passes, there are a front low pressure, followed by a thunderstorm high pressure and a wake low differing in intensity.