Previous studies focused on evaluation criteria, grouping them and using different techniques to evaluate maintenance systems. But the main question of this study was to determine the relationship between processes and objectives of maintenance systems to use of feedback from evaluation to improve the maintenance system and organization performance. This Research is a qualitative research approach that used the meta-synthesis analysis and Grounded Theory for analysis. Collecting qualitative studies related to research, analyzing findings, discovering the essential points and combined them into an overall alternative, to determine the characteristics of a model is done by meta-synthesis analysis. Then Grounded theory used for designing of the new model to assess the maintenance systems in the power industry. Finally, the designed model validated and approved by experts in the power industry and academic experts from the perspective of simplicity, flexibility and being understandable, practical and functional, integrity, focus and continuous improvement.