Abstract: In order to solve the problem that the traditional velocity measurement instruments can not be applied to Electric Multiple Units (EMU),because of the reverse of the flow and the limited space,a new type tube called T back-supported tube was developed.It has better total port.By the wind tube test,the correlation between velocity coefficient and the different varia-bles such as bend segment length,wind yaw angle,flow velocity and so on was discovered.A verification flow test of the flesh air tube in the full-scale experiment can prove its excellent char-acters.The best ratio between length and diameter of the bend segment is 2,and under this size, the velocity coefficient under the dynamic pressure 138Pa was only changed 1.34% as the pres-sure varied.The average velocity coefficient in the range of 353Pa of the dynamic pressure was 0.741.The wind yaw angle variation does have effect to the velocity coefficient of the T type back-supported tube.It is indicated that 10 degrees increasing can make the velocity coefficient decrease 6 .1 2%.The T type back-supported tubes were well applied in the EMU fresh-air tube flow testing;the errors between the testing results and the rated values were all within 4.02%. It is pointed that while the structure of the T back-supported tube is simple and symmetric,it is also less sensitive to the velocity and wind yaw angle variation.The tube worked stable and relia-ble and the result was also precise.