Abstract: To clarify the relation between turbulent dragreduction and self-excited vibration of flexible tubes, experimentswere performed on the effects of turbulent drag reduction and thecharacters of self-excited vibration,by comparing the turbulent drag with that in a rigid tube and by using adouble-sleeve structure and a laser displacement sensor. The resultsare as the follows: the thinner the flexible tubes, the larger the rootmean square of thefluctuating displacement at the outer wall of the tubes, and the larger thedecreasing rate of the friction coefficient of the self-excitedvibration, while applying a pressure-balanced air on the outer wall,with the rates of dragreduction of the flexible tubes with thickness of 2mm, 3mm, 4mm,being about12%, 10%, 9% at the Reynolds number of 17\,500. This would provide areference for efficient fluid transportation.