Abstract: Three dimensional configuration design of afterbody/nozzle was studied in this paper.Flow filed numerical simulations were conducted on NASA single expansion ramp nozzle experiment model.Numerical simulation results of two-dimensional and three-dimensional flow field without/with side fence were compared with experiment data and structure of three-dimensional flow filed.From the viewpoint of hypersonic vehicle airframe/propulsion integrated design,three-dimensional configuration of afterbody/nozzle was constructed with side fences.Parameters of cowl length and side fence inclination angle were investigated to analyze their effects on thrust,lift and pitch moment acted on overall vehicle.The results show three dimensional effect of afterbody/nozzle flow field could not be neglected.