The piezoelectric excitation property of multi-nozzle injector was studied by numerical simulation. Pressure

mass flow rate and fluctuation of velocity of the injector were obtained. The results showed that the pressure fluctuation was mainly influenced by wall motion characteristics

and the pressure amplitude increased with the increasing excitation frequency in multi-nozzle injector. But in the obturated cavity

the pressure fluctuation mainly depended on change of the cavity cubage

and the pressure amplitude didn't vary with the excitation frequency. Thus theoretical method of obturated cavity could not nicely forecast the pressure fluctuation in injector. In the multi-nozzle injector

the mass flow rate amplitude at inlet and outlet was different. The pressure amplitude distributed non-uniformly in different positions

resulting in different velocity amplitudes at multi-nozzle outlet

and also different jet shapes.