The evolution of work demands has seen industrial evolution itself evolve into the computerization of these demands, making systems more complex. This field is now known as the Complex Socio-Technical System. As communication failures are problems associated with Complex Socio-Technical Systems, it has been discovered that communication failures are the cause of many incidents and accidents in various industries, including the nuclear, aerospace and railway industries. Despite the fact that there have been many studies on the severity of communication failures, there is no evaluation method for operators' communication quality in Nuclear Power Plants (NPPs). Therefore, the objectives of this study are to develop an evaluation method for the quality of NPP Main Control Room (MCR) operators' communication and to apply the proposed method to operators in a full-scope simulator. To develop the proposed method, the Work Domain Analysis (WDA) method is introduced. Several characteristics of WDA, including Abstraction Decomposition Space (ADS) and the diagonal of ADS are the important points in developing an evaluation method for the quality of NPP MCR operators' communication. In addition, to apply the proposed method, nine teams working in NPPs participated in a field simulation. The results of this evaluation reveal that operators' communication quality improved as a greater proportion of the components in the developed evaluation criteria were mentioned. Therefore, the proposed method could be useful for evaluating the communication quality in any complex system. (C) 2011 Elsevier Ltd. All rights reserved.