The price for distributed generation system power connected to the grid is measured by its power quality in the future power market， therefore it is urgent to find an effective power quality comprehensive evaluation method. The power quality comprehensive evaluation for distributed power generation systems is studied. A hierarchical evaluation system for power quality is established， and a novel model for power quality comprehensive evaluation is proposed， where the catastrophe decision theory is applied. The proposed method has rigorous theoretical foundation， and it is easy to implement. In addition， it can eliminate the subjective factors during the assessment process. So the result is more objective and accurate. Finally， the feasibility and effectiveness of the presented method is confirmed by the measured data from a large wind farm.