"图案装饰法" can be translated as "pattern decoration technique" or "ornamental pattern method" in English, depending on the specific context and the nuance you want to convey.
"Pattern decoration technique" emphasizes the technical aspect of using patterns for decoration.
"Ornamental pattern method" focuses more on the method or approach of creating ornamental patterns.
Both are acceptable, and the choice may depend on the specific field or application in which the term is being used.