The geological condition survey, including subsea topographic survey and geological drilling survey, vessel type selection, including the selection of vessel volume and drag head, and construction technology selection and acceptance standards of the deep buried pre-trenching of submarine pipelines crossing channel are introduced. According to a specific project using layered construction method, the overall construction process is introduced. The methods of improving the construction efficiency, ensuring the construction quality and handling the area with excavation difficulty are summarized for reference of other similar projects, especially for the deep buried pre-trenching project of submarine pipelines crossing channel with layered construction method.