Abstract: An underwater acoustic propagation experiment was conducted in the Dongsha Sea to investigate the effects of upslope waveguide environments on sound propagation. The experiment revealed a significant attenuation of acoustic energy at the slope crest. A realistic waveguide environment model was established, and the parabolic equation theory was used to calculate the acoustic propagation loss, confirming the observed impact of the sloping environment on sound propagation. Ray tracing methods were further employed to discuss and analyze the mechanism behind the sharp decrease in acoustic energy. The results indicate that during upslope propagation in an environment with a negative sound speed gradient, the acoustic energy effectively reaching the slope crest varies significantly due to factors such as source depth, slope inclination, horizontal distance, and bottom sound speed. Shallower source depths, steeper slopes, and lower bottom sound speeds result in weaker acoustic energy propagation to the slope crest. Furthermore, compared to horizontal waveguides, increased horizontal distances in upslope waveguides lead to more pronounced acoustic energy attenuation.