On the basis of dividing identification region to the spatial error of the ballbar, the identification trajectory was generated based on the NUBRS spatial spline curve. The spatial identification principle of the ballbar was analyzed. An error identification model suitable for NUBRS space curve was established based on this principle, which contained 18 error factors. A space error identification method was proposed based on the multibody kinematics analysis results of fiveaxis machine tools. Through measurement and error compensation of the laser interferometer, on the basis of eliminating 9 spatial displacement errors, the generated NURBS curve was used to identify the remained 9 angle error factors. The experimental results show that after NUBRS curve correction, the method can be used to effectively identify 18 error factors in 3 coordinate systems.