The Gas Path Analysis method for fault diagnosis has be known as an effective method.But the crucial problem is the necessity of measuring a number of aerothermodynamic parameters more than or at least equal to the number of component fault parameters.But the number of measured parameters is always confined by cost and the structure integrity of the engine.The Sub-Matrices Analysis presented in this paper can perform component directed fault diagnosis with less measured parameters.The feature of this method is to combine the fault parameters into groups

in each of which the number of fault parameters equals the number of measured parameters to make the fault parameters solvable with respect to measured parameters.Thus

a set of solutions may be obtained.In order to select the most possible solution(s)

the criteria are also given.The numerical investigation shows that this method is very effective to diagnose the malfunction occuring in one or two components which is the usual case at an early stage of engine fault.The problems which are worth careful consideration to avoid false diagnosis are also pointed out.Application of this method to JT9D commercial engine verifies its effectiveness.