The feasibility of the multi-operating points gas path analysis (GPA) for engine fault diagnosis has been analyzed.The averaged error of estimation J is an effective criterion for determining the diagnosis accuracy.The recommended value of J has been given according to the numerical tests.It has been analyzed how the number of the operating points and the selection of the monitoring parameters affect the effectiveness of diagnosis.It is shown that the number of the necessary operating points can be significantly reduced and the diagnosis accuracy can be enhanced as the mointoring parameters are increased properly and selected correctly.Supplemental measurement of the pressure behind high pressure compressor and the pressure between high and low pressure turbines is a practicable measure for improving the diagnosis accuracy.