Abstract: In the shallow-sea environment, negative sound speed gradients and sloping seabed topography significantly enhance the multipath effect of the channel, which is prone to causing self-interference of communication signals and increasing the difficulty of topography inversion. Based on ray acoustics theory, this paper focuses on two scenarios (horizontally uniform seabed and sloping seabed with an inclination angle not exceeding θ) in the shallow-water channel with a negative thermocline. Within a receiving distance of 6.1 km, multiple configuration modes—where the sound source and receiver are located above and below the negative thermocline—are investigated, with emphasis on analyzing the influence laws of seabed inclination angle, transceiver distance, and sound source frequency on the multipath arrival structure. Simulation results show that: (1) In both horizontally uniform and sloping seabed environments, sound wave frequency and receiving distance have little effect on the pulse interval of the multipath arrival structure; (2) In the horizontally uniform seabed environment, the pulse intervals of the received signals under the "up-transmit–up-receive" configuration are relatively consistent. (3) In the sloping seabed environment, the first pulse interval of the received signal increases with the increase of the seabed inclination angle under the "uptransmit-upreceive," "downtransmit-upreceive," and "upreceive-downreceive" configurations, while it only increases with the receiving distance under the "uptransmit-downreceive" configuration. In addition, under the "uptransmit-upreceive" configuration for both horizontally uniform and sloping seabed scenarios, the theoretical approximate values of the multipath time delay difference show good agreement with the simulation results. This study provides a theoretical basis and application reference for signal pulse width design, trigger cycle optimization in communication systems, and seabed inclination inversion, as well as technical support for improving the anti-interference capability of communication signals and the accuracy of seabed topography inversion.