The biggest straightening force is one of the important parameters and has an important influence to straightening effect in the straightening process. In this paper, the numerical experiment of loading counterweight force was carried out by finite element analysis software in the steel tube bending. In bending straightening process of numerical calculation, two kinds of steel tube were selected, the size being Φ720mm, δ120mm and Φ325mm, δ55mm, respectively. The straightening force variation law of bending steel pipe was obtained under the plastic state trends in the straightening process. The best control parameters of steel pipe straightening have been identified for the steel pressure straightening and provide a theoretical basis for parameter determination.