Prediction and control of welding distortion is an important stage to guarantee manufacturing quality of steel structures. Thermo-elasto-plastic finite element method is employed to analyze the model of "U" rib orthotropic plate. Through this method, inherent strain in the weld zone is extracted. Inherent strain obtained which is regarded as known conditions is put on the weld zone of "U" rib orthotropic plate. Elastic finite element analysis is employed to predict the welding distortion of the plate. According to the prediction result, control scheme of welding distortion is made and a curvilinear equation is provided. The equation elaborates the shape of the welding jig controlling welding distortion. Numerical simulation method is applied to analyze the control scheme and the steps of the method are given. The numerical simulation result meets the quality request of welding deformation control. The method provides important reference for the control of the welding distortion in complex components.