Abstract: The probe used for transonic flow measurement should be calibrated in a wind tun-nel with Mach number from subsonic to transonic.The Mach number at the outlet of the slotted nozzle is changeable due to the self-adaptive effect of the nozzle in different backpressure.There-fore,the wind tunnel equipped with the slotted nozzle may be operated from subsonic to ultrason-ic for calibrating the transonic probe.For studying the performance of the slotted nozzle with wet steam as the working medium and optimizing its structure,detail numerical simulation is carried out by solving 3-D N-S equations and the realizablek-εturbulence model.The numerical results show that converging curve、divergent section length and slot size may affect flow field character-istic of the nozzle seriously.In a certain range of backpressure and inlet pressure ratio,there are optimal convergent curve,divergent length and slot size.According to the results of the numeri-cal simulation,a wind tunnel equipped with the slotted nozzle is developed.The Mach number of the tunnel with wet steam as the working medium may be continuously varied from zero to 1 .6 . The experimental results show that the flow at the outlet of the nozzle with such optimal struc-ture are uniform and stable in a wide range of Mach number from zero to supersonic.It is quali-fied to meet the requirements of transonic probe calibrating.