Abstract: Research on mechanical parameters of pipeline crossing by horizontal directional drilling is rare and the engineering is almost designed by experiential method. So there is a need to have more study on mechanical analysis of pipeline crossing design. In this paper, soil mechanical parameters in construction of pipeline crossing are analyzed and the new concepts of minimum required mud pressure and maximum allowed mud pressure are put forward. Then, the formulas of vertical soil pressure and mud pressure in the construction are given．Using these formulas，an engineering of pipeline crossing by horizontal directional drilling is analyzed and the quantitative values of soil stress and mud pressure are obtained. The theorization of mechanical parameters in pipeline crossing can provide the reference for the engineering practice.

Key words: pipeline, horizontal directional drilling, crossing, vertical soil pressure, mud pressure