A widespread severe convection weather in Shanxi on 24 April 2019 is analyzed based on a variety of observation data and NCEP/NCAR FNL 1°×1° reanalysis data. The results are as follows. 1) Under the background of weak synoptic scale forcing, this event is caused by the development of surface frontal cyclone and the extension of low-level northeast airflow into Hetao area, which trigger the development of one persistent elongated convective system (PECS) and one meso-β-scale PECS (MβECS). 2) On the radar echo, corresponding to the MβECS, there are many convective cells embedded in the whirling echo, while the PECS has 4 linear echoes and one heavy precipitation single-cell storm. Radar products can describe the characteristics of small-scale systems more precisely, but some typical characteristics of classified strong convection are not obvious. 3) The diagnosis of physical quantities show that the low-level frontogenesis not only makes the warm front trigger the development of MβECS and cause strong convection in the north of Shanxi, but also makes the cold front strengthen and the cyclone develop. The boundary layer jet and the surface mesoscale systems induce the merging, strengthening, and highly organizing of the convective cells in the central and southern parts of Shanxi. The range and intensity of strong convection are closely related to the scale of the vortex or convergence line and the convergence intensity of wind field. The disturbance characteristics of temperature, pressure, wind, and humidity field in the cyclone can better explain the physical mechanisms of the formation and development of the smaller-scale systems, and these characteristics appear one to three h ahead of severe convection and have a good indication for the nowcasting of severe convection. 4) The low-level northeast airflow acts as an inclined interface between dry and cold air and warm and wet air, on which various elements are not uniform. The formation of a cyclonic secondary circulation cell around this interface is an important trigger mechanism for mesoscale convective systems. The significant vertical shear of zonal wind on the both sides of this airflow is one of the important reasons for the propagation and long duration of convective storms.