Aiming at the problem of the influence of typical shallow sea environmental parameters on acoustic propagation loss，an improved coupled simple positive wave-parabolic equation model based on correction of reflection coefficient of seabed boundary is proposed. An acoustic propagation loss test in typical South China Sea waters is designed and carried. The relative error is less than 4% and the root mean square error is less than 3dB， which verifies the accuracy of the model. Then，five working conditions are designed for four marine environmental parameters，namely sound velocity profile，sea surface state，seafloor sediments and seabed topography，and simulation calculation and analysis are carried out. The results show that the sound velocity profile mainly affects the distribution of the acoustic convergence zone，and the energy of the acoustic convergence zone is mostly concentrated near the seabed and the depth of the sound source under the negative gradient，while the energy of the acoustic convergence zone is mostly concentrated near the sea surface under the positive gradient. The distribution of acoustic propagation loss in shallow sea environment is greatly affected by sea surface state and seafloor sediments. Seabed topography is the main factor affecting underwater acoustic propagation loss，and seabed slope can collect the energy of acoustic wave or disperse it.