Abstract: In order to reduce the wall interference and improve quality of the flow-field in a transonic wind tunnel, a set of variable porosity walls with 60° inclined holes have been designed and manufactured. The open-area ratio of the walls can vary continually from zero to 9.2 percent. The walls have been used in a 600mm×600mm tran- and supersonic wind tunnel with solid side walls.This paper describes the general characteristics of the variable porosity walls and the preliminary results of calibration at Mach numbers ranging from 0.6 to 1.2.