The invention discloses a method for measuring axial sound velocity of an in-use glass steel threaded pull rod in situ by utilizing echo and relates to a method for measuring sound velocity of a glass steel threaded pull rod. The method comprises the following steps of: (1) measuring screw pitch d between two adjacent threads on the glass steel threaded pull rod by using a vernier caliper; (2) inputting initial sound velocity C0 randomly to an ultrasonic flaw detector; (3) coupling and fixing a probe of the ultrasonic flaw detector to the end face of the glass steel threaded pull rod; (4) calculating distance d0 between two adjacent threaded waves by substracting soundpath 1 from soundpath 2; and (5) calculating the axial sound velocity CX of the glass steel threaded pull rod, wherein CX is equal to C0(d/d0). The method is simple and practical and is accurate in measurement. By the method, in-situ and on-line measurement is realized and efficiency is high. The method is applicable to measurement on the axial sound velocity of the in-use glass steel threaded pull rod. By the method, the technical problem that the axial sound velocity of an ultralong threaded pull rod cannot be measured by the conventional sound velocity measuring method is solved.