Natural gas hydrate was becoming more and more important in Chinese energy structure, which had the advantages of high gas content, low pollution and large reserves. Therefore, it was necessary to study natural gas hydrate. Aiming at the common blockage problem in transmission pipeline for natural gas hydrate, on the background of subsea level pipelines and based on the multiphase flow model, the calculating and analyzing natural gas hydrate mathematical model was established in gassolid two phase flow based on finite volume method. And the relationship was obtained between the difference of the diameter (the diameter of the pipe and the through-flow diameter) and the distance from inlet. When the inlet flow velocity and the diameter of the pipe were fixed, the stack position of the gas hydrate in the pipeline was analyzed with the difference of the diameter. Calculation results showed that with the other conditions remaining unchanged, as the increase of the distance from the pipe inlet, the change rule of the difference of the diameter was in accord with Gauss curve. Then the change rule was fitted and Gauss function equation was obtained, which could calculate the difference of diameter under a given position of pipe. Finally, through changing the diameter size of pipeline, the simulation and analysis were carried out, whose results showed that Gauss function equation also applied in pipelines with different diameters. A theoretical basis for predicting the stack position was provided in the pipeline and improving the transport efficiency of natural gas hydrate.