In order to solve the problem of assessment of cadets’ professional ability, puts forward a method for examination and estimation of cadets' professional ability based on optimum evaluation method. According to optimum evaluation method in extenics, use AHP to determine the index weight, establish professional ability evaluation index system, and adopt Delphi method to establish correlation function expression. Use scale valuation method to construct the relevant index judgment matrix, and select the best performers by optimum value, and verify it by example. The results show that this method can provide reference for improving cadets' professional ability and personnel training.