Abstract: An economic, flexible and automated operation and control strategy is the design objective of the advanced nuclear power plant. Adapting to this trend of development, the mechanical shim has been proposed recently. The mechanical shim is an advanced control strategy, which controls core reactivity and axial power distribution offsets by moving control rods. This paper studied the operation characters of mechanical shim in baseload, load following and startup/restart operation modes. The result shows that the mechanical shim can control the core automatically and keep the power peaking factors low in all operation modes, thus the mechanical shim is a flexible, effective and economic operation strategy. Moreover, the effect of mechanical shim on the nuclear power plant design was analyzed.