Abstract: It is always the key goal of current scientific research to build a rapid and accurate three-dimensional sound field model to meet the actual marine conditions. As a step-by-step solution method, the parabolic equation approximation method can obtain the sound field in the whole waveguide by stepping with the interval while the initial sound field is known, which is much convenient for dealing with the scenes related to the three-dimensional changes of the sound field and the horizontal changes of the sound channel. However, the computational complexity and calculation range in three-dimensional space are much greater than those in two-dimensional space, which seriously restricts the calculation accuracy and speed of the model. In order to improve the calculation accuracy and calculation speed of the existing parabolic equation model, the mathematical characteristics of the underwater sound propagation model is derived and analyzed in this paper. The distance, depth and horizontal azimuth angle are considered at the same time, which is named the three-dimensional parabolic equation model. Meanwhile, a parabolic equation model with higher calculation accuracy is proposed. By inserting a completely matched layer at the seabed boundary, the model is further improved. In addition, in order to reduce the time of three-dimensional sound field calculation, the parallelism of the model is studied. Based on the FOR3D serial algorithm, the parallel algorithm of three-dimensional parabolic equation model is developed with multi-threaded shared memory technology OpenMP. By comparing the running time with the ordinary absorption layer under different numbers of threads, the results show that the parallel algorithm based on the completely matched layer model has greatly improved in both the speedup and the calculation speed, which has practical engineering significance.