Abstract: The static pressure fields in an s shaped diffuser with rectangular cross section have been measured at different incidences.The results show that the static pressure field at the duct exit is non uniform.The higher the angle of attack is,the larger the distortion of the static pressure field.The pressure near the boundaries of the model is higher than that near the core,which is mainly caused by both the distorted total pressure field and the distorted flow velocity field.Further investigation on whirling flow field demonstrates that it is neccessary to take into serious consideration the deviation between the experimental measurements and the weighted averages by the use of the wall static pressures of the model at high incidence.