Abstract: Textile Machinery has many features as strong processibility, complex structure and many parts and so on. Conceptual design of textile machinery design, will inevitably encounter the coupling design problem. So a transforming bridge in extension theory was introduced to clear up the coupling problem. A decoupling method combining the fault tree analysis with extension theory was proposed. The formal description was made on coupled nuclear issue which was confirmed by the fault tree analysis. Hereby decoupling model and decoupling process of axiomatic design based on the conversion bridge was constructed. An example of vibration andtwisting winding system verifies the validity and feasibility of the method.