Abstract: A test system was established for the testing of the gas pressure in the Helmholtz type pulse-jet engine combustion chamber.The gas pulsating condition can be monitored in a real time manner.Number of impulse,stability of the pressure waves,etc.were used as indices to evaluate the stability of operation,and thus,the operating stability of the pulse-jet engine can be monitored and controlled during testing.The relations between the combustion chamber cylindrical section diameter and the parameters such as the gas pressure wave form in the combustion chamber,the working frequency of the pulse-jet engine,the specific fuel consumption and the excess air coefficient were investigated.It can be concluded that the diameter has no significant effect,but the opening of the throttle remarkably affects the parameters.