In order to solve the problems of variable working condition

non-linear and small sub-sample in the process of aero-engine health assessment

a variable precision rough set decision-making method based on the similarity measurement was proposed.Firstly

the principle and method of choosing value was given

and the decision-making rules were extracted.Secondly

the method of calculating attributes' relative importance based on cross-entropy was proposed and attributes' objective weights were given.Taking the expert experience and working experience into account

overall weights were formed.Finally

a weighted similarity measurement based on the overall weight of attributes was developed.By comparing the similarity degrees between the current object and other objects from the reduced decision-making system

the decision results were given.Simulation results show that the method is effective to aero-engine's health assessment with the help of expertise and running environment.In addition

the proposed method can be applied to other regions.