It has been observed experimentally that the signal waveforms in shallow water with thermocline have regular multipath structures and the waveforms of received signals are strongly dependent on the depths of the source and the receiver. When both the source and the receiver are located above the thermocline, each sigrtal received consists of a train of almost equispaced wave-packets. The time interval iswhere H, d, C0 and C1 are parameters of the sound velocity profile. When the source is below the thermocline and the receiver is above, the time intervals between wave-packets are τ and (T- τ)where η is the distance from the source to the bottom.These observed regularities of waveforms may be used for monitoring the fluctuation of the thermocline in shallow water. It has been observed experimentally that the signal waveforms in shallow water with thermocline have regular multipath structures and the waveforms of received signals are strongly dependent on the depths of the source and the receiver. When both the source and the receiver are located above the thermocline, The time interval iswhere H, d, C0 and C1 are parameters of the sound velocity profile. When the source is below the thermocline and the receiver is above, the time intervals between wave-packets are τ and (T-τ) where η is the distance from the source to the bottom. These observed regularities of waveforms may be used for monitoring the fluctuation of the thermocline in shallow water.