Three variables controller for aero-engine was studied in this paper.Given the fact that too many outputs of aero-engine could be used as controlled variables

and different controlled variables have varying performances

it is particularly important to get the suitable controlled variables.Here

the method of choosing best outputs as the controlled variables is RSCN(robust stability and condition number)method.Three output-variables were chosen from 14 outputs of aero-engine.After the selection of controlled variables was completed

an augmented LQR(linenr quadratic requlator) controller was designed.The simulation indicates that the controller with the chosen outputs gets very well dynamic and steady state performance.