The 3D target mirror is a vital part of micro / nano coordinate measuring machine system. The orthogonality between its any two mirror planes is very important to ensure the measurement accuracy of the measuring machine system. In order to verify whether the 3D target mirror meets the accuracy requirement of the measuring machine, the orthogonal deviation angles of the 3D target mirror are measured and the measurement uncertainties are evaluated. On the basis of quantitative characteristic analysis and modeling, the traditional method (called as GUM method) given in the guide to the expression of uncertainty in measurement, Monte Carlo method (MCM) and adaptive Monte Carlo method (AMCM) are researched. The comparison of the measurement evaluation results shows that the 3D target mirror approximately meets the accuracy requirement of the measuring machine. The orthogonal deviation angles of Z-X mirror planes and Y-Z mirror planes are about 0. 5″, and the orthogonal deviation angle of X-Y mirror planes is about 3. 3″. The evaluation results obtained by the three methods are basically consistent. Moreover, MCM and AMCM are more reasonable than GUM, and AMCM method is more efficient than MCM method. This work provides reference methods for the task-oriented measurement uncertainty evaluation of micro / nano CMM.