The invention provides a bonding method of a tramcar roof made of a light composite material, and belongs to the field of connection methods of railway vehicle light composite material car roof structures and car body steel structural skeletons. According to the method, the bonding property is improved by conducting surface treatment on the surface of the light composite material, bonding glue suitable for the light composite material is selected, fixing and limiting methods which cause less damage to the surface of a light composite material plate and are light and accurate are adopted, the environment condition of construction is adjusted, the solidification time is shortened, and thus bonding of a car roof component made of a light carbon fiber composite material and a car body steel structure is achieved. As the replacing technology of the welding technology, the manufacturing method of the car roof component by adopting the bonding method is simple, convenient and practical, and safe and reliable, the bonding strength completely conforms to the design requirement, and the light carbon fiber composite material can be successfully applied to the field of production and manufacturing of railway vehicles, accordingly the total weight of the car body is sharply lowered, the production efficiency is greatly improved, and the power nuclear energy sources needed by operation of the vehicles are saved.