A diagnostic analysis was made of a local lasting heavy rainstorm took place in the central part of Shaanxi Province on 28 June 1994. The heavy rainstorm appeared in the front of a 500 hPa trough near the shear line of a depression on the 700 hPa, happened in the superposed zone between the right divergence area around the entrance of the upper-troposphere jet and the left convergence area of the lower-troposphere jet, and was related with the mesoscale cyclone on the surface. The diagnostic results show that the mesoscale cyclone on the surface was caused by the sub-circulation resulted from the coupling of upper and lower jets and the sub-circulation controlled the development and change of mesoscale systems.