Abstract: Through the process analysis of determining engine thrust and converting engine thrust of the simulated altitude test,the application mechanism and its applied conditions of the "nozzle blockage" technique in the simulated altitude test of aero engine with the convergent nozzle are clarified.By means of the result analysis of the "engine jam" experiment on Spey engine in the simulated altitude test facility of the Rolls Royce company and on turbojet engine in a simulated altitude test facility,the application feasibility and its rationality are made clear of the "nozzle blockage" technology in the simulated altitude test of the aero engine with the convergent nozzle.The research results extend the workable and applicable scope of the thrust calculation and correction formula of HB6213,which stands for the performance correction standardization of the altitude simulated test of the turbojet and turbofan engines.