There was a regional heavy rain in the middle of Shannxi Province at the night o f June 2, 2006. The rain was analyzed by using Doppler data. The result shows t hat the mesoscale convergence line, which was the result of interaction betwee n the lowlevel warm/wet jet and weak cold air, directly produced the heavy rai n. Lowlevel jet provided not only ample of vapor but also instability energy , so it was the main matter which resulted in so heavy rain. The directions of lowlevel jet and mesoscale convergence line that affects the developing of convergence line. At the night, lowlevel jet will become more intensive, that is why lots of heavy rain occurred in the evening.