The NCEP 1° × 1° reanalysis data，FY － 2E satellite images，conventional meteorological data，and the method of combining satellite cloud images with atmospheric dynamic field were used to analyze the dry intrusion characteristics under the influence of cold eddy and the role of the dry intrusion during the short － time strong rainfall which occurred in Yulin of Shaanxi Province on July 15， 2012． The results show that the characteristics of the dry intrusion was significant during the short － time strong rainfall process，the high value area of TBB on satellite water vapor images corresponded to the dry cold area of upper troposphere，while the stretching of the cold dry area made the TBB gradient on convective cloud edge increase，at the same time convective cloud developed． The dry intrusion corresponded to the sinking motion，high value area of potential vorticity and dry cold areas in the upper troposphere，the instability stratification appeared over the heavy rainfall region due to the dry cold air overlaying the warm wet air，which created favorable environmental conditions for the occurrence of the short － term heavy rainfall． In addition，water vapor of the rainfall process mainly concentrated in the lower troposphere，short － term moisture convergence caused by wind convergence created a favorable moisture condition for the short － term heavy rainfall． The lifting of air mass that contained water vapor caused by the trigger mechanism of mesoscale convergence line on the ground led to precipitation．