The present study aims to explore dynamical behavior of the fluid- elastic vibration of a single cylinder and three cylinders in shear flow by numerical simulations. This paper investigates the effects of the shear parameter, mass ratio, and spacing(P/D) on fluid-elastic vibration of the cylinders. Continuity equation and momentum equations are solved alternatively using a CFD package, Fluent 6.3.26. Dynamic meshing techniques together with the cylinder motion equations are employed in the simulation. Under different flow conditions, flow types, and cylinder motion models, lock-in and fluid-elastic vibration are studied. The results show that motion and flow types of a single cylinder in uniform flow are in agreement with the previous studies in literatures. In shear flow, however, as the shear parameter increases, the fluid-elastic vibration of the cylinder is induced, and thus amplitude of the cylinder increases considerably. Further, three cylinders in the shear flow are studied. Three cylinders arrangements (classified as side-by-side, tandem ,and stagger) and the distance between cylinders are the factors to cause fluid-elastic vibration. Compared with the single cylinder motion, three cylinders motion¡¦s critical flow velocity is smaller than that of the single cylinder motion, which means two cylinders motion are more subject to fluid-elastic vibration.