The invention provides a method of making a pattern on a building on site, which comprises following steps: applying a base coat on a surface of said building; pressing and adhering a pattern mold onto said base coat before initial setting of said base coat so as to form a compound body of the base coat and the pattern mold; applying a cover coat on said compound body; releasing the mold so as to obtain said pattern. The decoration method of the invention makes the wall surface safe and solid, of a long service life, available of a variety of patterns and convenient to construct.