The responses of main building under different strong earthquakes, such as El Centro, Taft, Wenchuan-Jiangyou were compared, and dynamic time history analysis based on Wenchuan-Jiangyou record with different peak values was used to reveal the damage mechanism of this typical structure. The results indicate that the response of Wenchuan-Jiangyou record is the smallest, but variability is the biggest. Wenchuan earthquake, which is more than design intensity, does not cause serious damage of main building. The torsional effect is remarkable, and coal scuttle layer is always weak layer. The stiffness degradation of frame is faster than the bent part, and the proportion of bent part within total earthquake action is enhanced firstly and then remains same. But the overall proportion is still in low level and bent part is unable to become the second resistance component. Although space grid roof system in turbine hall does not collapse because of strength failure of components, the bearing carries over huge shearing force with oversized distortion, and the failure of bearing will lead to collapse of roof system. Plastic deformations mainly concentrate in the first floor and coal scuttle layer, and “strong beam and weak column” are exposed.