To investigate the local structure of the (CrF6)(3) cluster for Cr3+ in Cs2NaAlF6 and Cs2NaGaF6, the unified calculations of the whole EPR, optical spectra are made based on the 120 x 120 complete energy matrices which are constructed on the basis of the complete set of the basis vertical bar J, M-J >. The results demonstrate that Cr3+ substitute for the two inequivalent M3+ sites rather than the Na+ or Cs+, which accord with the conclusion of several experiments. Simultaneously, the local structure parameters are determined and the relationship between the structure and the temperature has been discussed. (C) 2008 Elsevier B.V. All rights reserved.