Abstract: Based on ground conventional observation data and intensive automatic station observation data, cloud image of FY-4A satellite, Doppler radar data, wind profile radar data and ERA5 reanalysis data, a short-duration extreme rainstorm which broke the historical record in southern Guizhou on 29 May 2022 were analyzed from formation process and mechanism. Results are as follows: (1) The short-duration extreme rainstorm was caused by the combination of medium-β scale vortex and topography under a typical low-trough cold front type. Before the convection, the abnormally high precipitable water of the whole layer, the strong water vapor convergence in the lower layer and the significant vertical water vapor lapse rate provided favorable water vapor conditions for the short-duration heavy precipitation. (2) The strongest precipitation occurred in the formation and maintenance stage of MCC, and the change of TBB intensity was consistent with the change of precipitation intensity, the lowest value of TBB and the strongest precipitation in 10 min occurred at the same time. The rainstorm center area was affected by the herringbone shape echo and several strong echo units with low quality cores repeatedly, resulting in short-duration extreme heavy rainfall. (3) Convective cells developed along the front and frontogenetic regions, the prefrontal statically unstable stratification, convergence at low level and divergence at high level made the convection maintenance and enhancement. The combined influence of medium-β scale low vortex, cold pool and topography also provided the maintenance conditions, the main reason for forecast bias was insufficient consideration of the effects of medium-β scale low vortex, cold pools and terrain.