It was only about two decades that horizontal directional drilling crossing was introduced into China as a type of trenchless technology, which was rapidly developed in this period. As urbanization was accelerated in China, and along with the intensity of large-scale infrastructure construction projects increased, more and more large-scale projects of pipeline crossing were carried, but risk assessments on these projects are still few. The paper introduced a largescale gas pipeline project with large amount investment and serious risk; the risk assessment prior to project construction is necessary. Firstly index system was established based on the project evaluation by the experts, then the synthesis of advantages of fuzzy comprehensive evaluation method and AHP (analytical hierarchy process) was adopted and according to the evaluation data, the judgment matrices and membership matrices of this index system were built; and the weight vectors and membership vectors were calculated by Matlab programming, risk value of the project was obtained and the corresponding conclusions was drawn.