Research purposes ： In order to research the damage of bridge piers，which was caused by the rockfall in our western mountain area，based on the damage constitutive model proposed by HJC，the damage of double - column pier under the impact of rockfall was analysed by the nonlinear explicit dynamic software LS - DYNA according to the typical bridge pier on Dujiangyan to Wenchuan Road. And the degree of pier damage was analysed by changing impact height， velocity，eccentricity，impact angle，impact surface and the rock diameter. Research conclusions:(1) The rock diameter and velocity were the parameters with the most influence on the damage volumn rate of bridge pier. It indicated that the more energy rockfall had，the greater damage bridge pier was suffered. The energy parameter E which included diameter and velocity， should be adopted to be the reference on damage of impact. (2 ) Adding steel plate tube and thickening concrete protective layer should be adopted to reduce the damage of rockfall to bridge pier on Dujiangyan to Wenchuan Road. When the potential energy of rockfall was too big，a further active protection measure，such as protective nets and protective railings， should be taken to avoid the damage of the whole components. (3) This research results can be used in guiding for the design of protective measures for mountain bridge piers under impact of rockfall.