Cleaner production assessment is an essential part of cleaner production methodologies. To date, a number of different methods have been developed for or applied to cleaner production assessment. Although there is no inherently better or worse tool, cleaner production assessment should fully consider the inherent attributes of cleaner production itself. One prominent attribute of cleaner production is the relativity of cleanliness, considering it made cleaner production assessment more understandable. Meanwhile, the relativity of cleanliness caused another unresolved issue in cleaner production domain, namely, how to cope with the inconsistent-baseline-technologies and multi-baseline-technologies. This research was intended to propose a cleaner production assessment model that considered the relativity of cleanliness and solved the inconsistent/multi-baseline-technologies issue simultaneously. Considering the prominent attributes of cleaner production, the reduction rate of pollutant generation or resource consumption was chosen as the cleanliness level index, making cleaner production assessment more understandable; by employing a baseline technology determining vector, this model realized cleaner production assessment under inconsistent/multi-baseline-technologies, making the assessment more practicable. The feasibility and applicability of this model were demonstrated by a case study of coal-fired power generation industry. The results demonstrated that comprehensive assessment could be simplified by downsizing the index system.