Abstract: The acquisition of decisions based on maximal distribution is one of important aids in aero-engine fault diagnosis,and consistent-approximative denoted space(CADS) offers a tool to uniformly process them;and,aero-engine fault is a typical problem of small samples set.Aimed at decision-making information system of a certain aero-engine fault,the paper firstly sought its CADS based on maximal distribution,then introduced the method of rule fusion to obtain all decision rules under different conditions,and the history faults were recognized accordingly with a higher rate of identification.The result shows the effect of this method and the applicability of the decision-rules received from rule fusion.