The error modeling and compensation technology of the straightening machine were researched. First of all, the straightening machine was considered as a multibody system structure. The structure description of the machine tool and the coordinate system between the adjacent moving parts were established. Secondly, the geometric error model of the machine tool was derived by the second transformation matrix body system,and the geometric position error of the machine tool motion axis was identified by the laser interferometer based on the error model. Finally, the identified errors were compensated by the error compensation software and the error compensation test. The error compensation effect was evaluated by experiments.The experimental results show that the error model is correct and the software compensation is feasible.