Shedding vortices in cross flow are of much practical importance in the analysis of flow induced vibrations of a steam generator. However, studies of shedding vortex are still few in present, especially in shedding patterns and its influences on lift performances. In this paper, five basic shedding patterns were investigated by numerical simulations of a 2D unsteady flow around a bundle with 253 cylinders. The numerical results clearly demonstrated that flow in line is the most common pattern. On the hand, the other four shedding patterns, cross in line, cross near line near, cross near line far and cross far line near, appear randomly. Influences of shedding vortices on lift performances were concluded as lift enhancement, lift pit and lift lag. These numerical results can provide a basic knowledge of shedding vortices for cylinders and can precisely quantify their influences on unsteady lift performances.