In order to probe the mechanism on friction reducing effect by coupling of flexible tubes with turbulent flow, experimental investigation  was performed on effect of turbulent drag reduction, fluctuating vibration characters of tube  outer wall and the relations between them, based on experimental examination of effect of turbulent drag reduction in flexible tubes by  comparison with turbulent drag in rigid tube by using double -  sleeve and laser displacement sensor. The results were found as the follows: the thinner the flexible tubes, the bigger the root mean square of fluctuating displacement at outer wall of the tubes, the bigger non -  dimension burst period and the bigger the decrease rate of friction cocfficient by coupling of flexible tubes to turbulent flow. When  apply pressure -  balanced air on the outer wall,the non -  dimension burst periods of the flexible tubes with thickness of 2 mm, 3 mm, 4 mm, are 141,126,105 at the Reynolds number of about 17 500, respectively. This would offer an experimental technical selection for technological development of efficient fluid transportation.