Abstract: Robust design involves mainly parameter design and tolerance design．Minimum sensitivity model is applied to determine the nominal value of design parameters，while the minimum deviation model is used to determine the tolerances．These two models constitute the new approach of robust design based on key characteristics．With this approach，not only the values of design variables are worked out to ensure the stability of product quality，but also the tolerances of design variables are set up to meet the requirements of product functionality．Case study of a three bar mechanism with programming on Matlab verifies the feasibility and effectiveness of this approach．