The invention discloses a multifunctional tool for surface finishing and slope finding of foaming concrete and a construction method. The tool comprises a towing rod and a surface polishing template,the front end of the surface polishing template is provided with a clamping groove, and a leveling device and a scraping device are detachably mounted in the clamping groove; drawing devices are mounted in circular holes of the lower end of the surface polishing template; a night-vision level ruler is mounted at the upper end of the surface polishing template; a retractable graduated scale is mounted on the portion, close to the surface polishing template, of the towing rod; a spring connector is mounted at a connection section of the towing rod, and a slope controller is mounted on the portion, at the front end of the spring connector, of the towing rod. According to the multifunctional tool for surface finishing and slope finding of the foaming concrete and the construction method, a setplane for construction can be searched for through the leveling device, a slope point does not need to be manually searched for in the construction process, the construction is more convenient, and the work efficiency is improved; the tool is easy to manufacture and convenient to operate, and the labor and materials are saved while it is ensured that the construction requirements are met.