In view of the influence of the machining global deformation on the machining accuracy during the machining process of large storage tank bottom，the machining global deformation of the curved surface of large storage box bottom is predicted and analyzed，and the compensation method for the corresponding machining error is investigated.Based on the thin shell theory and energy method，an analytical model for the machining global deformation of the curved surface of large storage box bottom is established，and a deformation compensation method based on area division and virtual reference point coordination is proposed.A finite element model is established to predict the machining global deformation of the curved surface of large storage box bottom.The machining process is simulated，and the machining error compensation value is determined according to the predicted deformation results.Machining tests are carried out，and the obtained on-machine data verify the reliability of the model.This indicates that the proposed method can accurately predict the global deformation of the storage box bottom components，and the compensation machining based on the predicted results can effectively improve the machining accuracy and efficiency.