Abstract: Aiming at the topic of source depth discrimination in shallow water. An approach which is used to extract the relation items of modes from the received signal's relation formula by warping transform is present. The received signal's relation formula is warped to obtain its relation items of modes. Using the proportion relationship between the characteristic frequencies of the relation items whose energy is dominant to determine the numbers, the depth of the source can be identified. The formula derivation and simulation results provide that the characteristic frequencies of the relation items aroused by sources in different depths are not the same. The experimental results prove its effectiveness.Under the condition of approximate constant velocity profile and low frequency, the method can be used to determine the depth of the source by extracting the relation items of modes and recognizing its number, in the case of unknown sound source range. The movement of the source is not necessary.