The invention discloses an acoustic flow measurement device and a method thereof. The acoustic flow measurement device is adopted between observation stations for sending sound waves to the opposite side simultaneously, then receiving sound waves transmitted by the opposite side, the bidirectional propagation time of the sound waves between the two observation stations is obtained by calculating; the difference and the sum of the acoustic signals bidirectional propagation time are used for reversing the mean velocity and the average temperature between observation stations. The invention can carry on the vertical sample based on sound propagation multi-path effect by only using a pair of sound-source-receiver; as the ocean interior images can be obtained by observing the external measurement of the sea; compared with the traditional method, the synchronous measurement with the large-scale and long time between two points by using a pair of instruments can be realized; the collection performance of the sound propagation can obtain ocean environment parameters with the vast scale in space and the average time which can not be obtained by the traditional point sensor; the method solves the problem that the observing is affected by shipping and fisheries activity.