Conjunctive multifreeform surfaces (CMFSs) play an important role in many advanced optical systems. The position and posture accuracy of freeform surfaces are the key to system performance. However, there is no effective method of measuring the positions and postures of multiple freeform surfaces. In this study, a CMFS measurement system based on multisensors is developed, and a trust region registration based on the least squares method is proposed, with the aim of registering multiple freeform surfaces at different positions and postures. The performance of the proposed system was analyzed and the errors were calibrated. The calculation accuracy of the registration method was within 20 nm at $\Phi 50$ mm in terms of root-mean-square (rms) values. The positioning accuracy of the freeform surface measurement system proved to be $1.2 \mu \text{m}$ within the area of $120\times120$ mm; the related uncertainty was also analyzed. The proposed measurement approach provides a comprehensive solution to optical CMFSs.