Abstract: Based on fussy set theory, a quantitative method for welding geometrical quality control of precision welding structure (PWS)is presented.The "Quality Differentiation Coefficient" which characterizes the relation between quality difference and effective quality essentials is adopted to formulate the qualitative linguistic variables of welding quality difference properties.The welding quality analysis model which could fully utilize experts experiments and historical data for PWS is established to quantificational analysis and decision-making.