Abstract: In 1995,a new,compact and efficient method to stabilize flame,referred to as Trapped Vortex concept,was introduced firstly by K.-Y.Hsu,a professor of Dayton University.For obtaining good performance characteristics in a trapped vortex combustor,the fluid dynamics should be studied in depth.On the basis of former research work,a numerical investigation and experimental research work were performed for understanding the relationship of trapped vortex characteristics and pressure loss varying with the diameter afterbody (Da) and the length of centerbody (H) under cold environments when the diameter of forebody and the inlet annular velocity are fixed at Df=70 mm and Ma=03 respectively.The results show that within the range of Da/Df=05～08,each value of Da/Df corresponds to a specific optimal H/D (02～20),when a stable vortex is trapped in the cavity.The characteristics of this trapped vortex,mainly the vortex core and vortex area,meet the requirements for the injection of fuel and primary air introduction.In addition,a minimum pressure drop is achieved across the combustor.