The multi-cell storm in northeast of Huabei Region and squall line in Huanghuai Region happened under the same circulation background of northeast cold vortex on 22 August 2015. Based on meteorological observation data, this paper first shows the dynamic and thermodynamic effects of largescale cold vortex on the development of mesoscale convective systems. Then, based on the results of WRF mesoscale numerical model simulation, the differences between shape structure evolution and movement process of the two convective systems are compared. The reasons for structural evolution differences and effect of cold vortex are analyzed as well. The research suggests that: (1) Both of the two convection systems are located behind the cold vortex, but their shape evolutions of the two mesoscale convective systems are different. The northern convection was impacted jointly by surface winds and uplift of terrain, forming a multi-cell storm with a northwest-southeast alignment. It traveled slowly south-southeast by downwind propagation, bringing short-time severe rainstorm. The southern linear convection was formed by combination of several isolated cells which formed in northwest of Shandong and north of Henan. Later, the linear convection developed in Huanghuai Region into a squall line system, which moved rapidly to southeast under the action of advection movement, resulting in thunderstorm and hail. (2) The northern multi-cell storm formed in the interface of cold and warm air masses, located in the southwestern quadrant of cold vortex with sufficient low-level water vapor and energy. After being triggered by the boundary layer, the new convective cell propagated along lower shear line to the high-energy zone. (3) The southern squall line system formed in low pressure belt of surface warm area behind cold trough. Cold pool and outflow of thunderstorm high pressure generated by mesoscale convective system interacted with the environment, causing cell to continue to spread, merge and develop into a squall line system. (4) The intensity of mid-level rear inflow and water vapor condition had significantly different effects on the organization of the two convective systems. The increase of rear inflow of squall line in middle layer mainly came from the increase of westerly component, which was related to enhancement of environmental wind field caused by evolution of cold vortex. The mid-layer wind field where the northern convection was located was weak and the whole layer was wet, which was not conducive to the development of multiple cell storm organizations. The middle troposphere of south squall line was located in westerly steering airflow which was stronger than the northern convection. The inflow was strong and ambient air was dry, favorable for the formation of strong descending airflow, enhancing the development of thunderstorm high pressure and cold pool. Strong downdraft increased wind speed in middle and lower layers and enhanced vertical wind shear, which is conducive to the development of convective cell organization and formation of linear convection.