Abstract: A passive ranging and velocity estimation method, using the sound field interference characteristic, the waveguide invariant and a single moving hydrophone array, is proposed. A variant of a moving target, termed as the ratio of the range to the range varying rate(RRRVR), is defined, which is dependent on the sound field interference characteristic and the waveguide invariant. Accordingly, by using the Radon transform, RRRVR is estimated from the time-frequency interference image of the target sound field. And finally, the target range and velocity are estimated from RRRVR, the moving speed of the array platform, the target angle and the target heading angle. Numerical simulations are given to demonstrate the correctness and the effectiveness of the proposed method. The results show that the accuracy of the proposed method on the passive range and velocity estimation is at a high level when the target heading angle is relatively large; and a smaller target bearing estimation error ensures a higher ranging and velocity estimation accuracy.