The distribution characteristics of the airflow field have obtained by Laser Doppler Anemometer (LDA) in the cross-section of the sudden enlarged roadway,which belongs to the non-contact measurement te chnology to solve the limitations of traditional contact instantaneous velocity measurement.Experiments show that the airflow di stribution is symmetrical in the straight roadway before the sudden enlarged roadway,and the backflow zones exist in the upper an d lower corner of the sudden extension with asymmetric distribution;From the view of the wind speed distribution of the cro ss-section on the longitudinal axis,the wind speed of the cross-section shows the “Ω” type distribution trend in the backflow zone ,while the wind speed distribution is symmetrical on the horizontal axis,which is not affected by the sudden enlarged section;The wind speed contours show a ring-like distribution in the full section.And the wind speed distribution characteristics present a slightly prot ruding form at the corners of the cross section in the sudden enlarged roadway because of the turbulent secondary flow in rectangular p ipe.The study illustrates LDA as a non-contact measurement technology provides a feasible experimental means for the study of t he complex turbulent characteristics of the flow field in the mine ventilation t unnel.