Preliminary investigation of combustion efficiency under low pressure was carried out.This study is aimed at investigating the enhancement of combustion efficiency using the hybrid multistage swirling cup.The hybrid multistage swirling cup was made up of a pilot simplex nozzle combined with airblast atomizer.A single nozzle combustor was fabricated for combustion efficiency test.Combustor inlet velocity and overall fuel/air ratio were simulated under low pressure condition.The gas sampling was used for the combustion efficiency measurement.The results show that the hybrid multistage swirling cup can improve combustion and enhance combustion efficiency with combustor inlet pressures ranged from 0.07 MPa to 0.11 MPa.