The invention discloses a method and system for measuring propagation speed of natural gas pipe leakage vibration wave. The method and the system are on the basis of an optical fiber sensed natural gas pipe leakage monitoring method. A natural gas pipe leakage monitoring system selects a known sensing unit point to simulate pipe leakage in the form of hitting a pipe to initiate vibration; according to the number of pipe sections used in project construction and inspection and acceptance data, leakage signals transmitted to two adjacent sensing units are subjected to time-delay estimation; leakage vibration wave speed is measured by combining known pipe length; the distances from the current test point to two adjacent sensing unit points are accurately obtained; a simulating test point X is substituted into the formula that X is equal to L-[v*(tn+2-tn)]/2 to inversely solute the formula that v is equal to 2(L-X)/(tn+2-tn); and the propagation speed of vibration wave along the pipe is measured according to the distance between known sensing units and detected signal transmitting time. The method and the system are high in sensitivity and accuracy, and low in false alarm rate and are not easily affected by environmental factors.