Abstract: From the weather background, combined with Doppler radar data, the author analyzed the weather situation in May 6, 2015. The results showed that: (1) The process mainly for the northeast cold vortex type, with the lower shear dry wet unstable stratification, resulting in from the northwest to the convective clouds above Shanxi and Henan Province will continue to strengthen the development, and ultimately the formation of the squall line storm. (2) atmospheric stratification instability in the index K, Cape value, index (SI), strong vertical wind shear, near surface inversion layer exhibited significant, 0 and - 20 ℃ layer height also has benefit to hail. At the same time, the vertical structure of the cold and warm advection made the atmosphere more unstable. (3) >60 dBz strong echo center successively evolved in the form of “bow echo-squall line-cross the ‘people’-shaped echo-squall line”, the convection development in the top position of “people” was the most exuberant. (4) The process was storm group with squall line. Along the radar direction there was a very obvious “V” type gap and three body scattering, the three body scattering sustained about 2 hours, the echo characteristics was the strong echo hang in low layer weak echo area. (5) Echo top height was 11 km and had wide range. The process was a number of storm group composed by super monomer storms, which had big intensity, wide area, long duration, it was rare in history.