Errors of structural parameters are one of the main factors causing uncertainty of articulated arm coordinate measuring machines (AACMM); therefore the accuracy of AACMMs can be improved efficiently by structural parameters identification. The homogeneous transformation equations of 6-DOF AACMMs were established based on Denavit-Hartenberg model. A method to identify structural parameters with a cone-shape hole was analyzed. A modified simulated annealing algorithm (MSAA) was presented to identify the structural parameters of the AACMMs. The MSAA can keep the best solution during search

and reduce the search range when the solution approaches the global minimum

which can improve the search efficiency and accuracy. The definition of single-point repeatability was deduced

and the method using single-point repeatability as the objective function to identify structural parameters of AACMMs base on the MSAA was presented. A 6-DOF AACMM was used to carry out experimental tests to evaluate the efficiency of the method presented

the results show that after identification the repeatability and length measurement accuracy of the AACMM are improved 7.87 and 5.59 times respectively.