To realize the high-precision position measurement of freeform surfaces， this paper proposes an optic-mechanical reference positioning method that employs a position measurement model. First， an optical-mechanical reference positioning method based on a coordinate measuring machine and computer-generated holography is proposed. Then， using a spherical mounted retroreflector （SMR） target ball， cat eye， and reference ball as the benchmarks， three benchmark position measurement models are established on the basis of wave aberration theory and parallax effect. The functional relationship between the position error and the wavefront aberration in the reference area is obtained， and the three position measurement models are compared and analyzed. Finally， the three benchmark position measurement methods are simulated and validated via experiments. The residual difference between the measurement results and the model is below 0.05λ， and the relative error is below 2.43%， confirming the accuracy of the model. The experimental results indicate that the axial positioning error of the cat-eye method is 24 μm when the measurement distance is 1 000 mm. The axial positioning error of the reference-ball method is 50 μm. The SMR target ball positioning error is 16 μm in the axial direction， 1 μm in the X and Y directions， and 3.26″ in clocking. The SMR target ball method has the minimum positioning error， maximum measurement dynamic range， and maximum degree of freedom in detecting optical elements； therefore， it is more suitable for high-precision pose measurement of freeform surfaces.