Abstract: Taking the No.1 Petroleum Plant of Fushun Petrochemical Corporation as an example, with the analysis on the foundation deformation mechanism under the open pit mining, the paper stated the deformation direction causes of the plant area were the open pit mining and the major influence factors were the crack structur es and the underground water.Based on the study on deformation subregion, with the practices, the actual control general ideal and the prevention and control measure s suitable for the plant area were searched.In combination with the regional deformation features and the building structure features, underground water sealed curtain grouting, underground empty crack backfill grouting, underground mixed pile continued wall reinforcement and building structure reinforcement, deviation rectification a nd other measures were individually applied to reduce the foundation deformation over 30% and to ensure the safety of the plant area.