Abstract： The states of manufacturing resources can be monitored and assessed through the amount of information needed to describe their technological structure and operational state from an information-theoretic perspective. The amount of information needed to describe cellular manufacturing systems was investigated by two measures, the structural entropy and the operational entropy. The structural entropic model and the operational entropic model were developed based on the Shannon entropy, respectively. Scheduling was introduced to measure the entropy models of cellular manufacturing systems and the feasible concepts of maximum schedule horizon and schedule adherence were advanced to quantitatively evaluate the effectiveness of schedules. The conclusion shows that the states of cellular manufacturing systems can be measured and monitored and effective ways can also be provided for improving operational efficiency of the systems by the entropy models built.