To study the effect of the troposphere-to-stratosphere transport (TST) caused by severe convection and the associated background synoptic system, two severe convection events, one that occurred at low latitude and one at midlatitude, were simulated. In the low-latitude case, in Guangxi Province, the proportion of TST caused directly by severe convection was about 18%, while the TST caused by the synoptic background system of the severe convection was about 82%. In the midlatitude case, in Hebei Province, the proportion of TST caused directly by severe convection was about 0.17%, while the TST caused by the synoptic background system of the severe convection was about 99.83%. In terms of the motion of particles transported from the troposphere, the particles transported directly by severe convection moved towards the southwest in both events, while the particles transported by the synoptic background systems moved towards the east. In general, the amount of TST caused by the synoptic background system of the severe convection was much larger than that caused directly by the severe convection. The TST caused by the synoptic background systems occurred two days after the severe convection initiation and reached a maximum six or seven days later.