Abstract: The field investigation of forestland usage for projects is an important part of forest resource operation design and investigation work. This article discusses in detail the various aspects of national level protected plant investigation work involved in the forestland usage for projects, including the causes of investigation work, preparation for field investigation, methods of plant protection investigation, investigation content, technical means, organization of investigation results, and report writing. It analyzes and elaborates on the technical problems and difficulties that arise in plant protection investigation. The application of survey techniques and methods to the actual use of forestland usage for projects can help further standardize the content of national level protected plant surveys in inventory of protected plants, and can serve as a reference for the survey of national level protected plants in forestland usage for projects.